[Windows] Add target architecture to build path (#131843)

To implement windows-arm64 support, it is needed to add architecture as a subdirectory (https://github.com/flutter/flutter/issues/129805).

In short, when performing a flutter windows build, we have:
- Before: build/windows/runner/Release/gallery.exe
- After: build/windows/x64/runner/Release/gallery.exe

This convention follows what flutter linux build does.

Addresses: https://github.com/flutter/flutter/issues/129805
Addresses: https://github.com/flutter/flutter/issues/116196

Design doc: [flutter.dev/go/windows-arm64](https://flutter.dev/go/windows-arm64)

dev/a11y_assessments/windows/flutter/CMakeLists.txt

@@ -10,6 +10,11 @@ include(${EPHEMERAL_DIR}/generated_config.cmake)
 # https://github.com/flutter/flutter/issues/57146.
 set(WRAPPER_ROOT "${EPHEMERAL_DIR}/cpp_client_wrapper")
 
+# Set fallback configurations for older versions of the flutter tool.
+if (NOT DEFINED FLUTTER_TARGET_PLATFORM)
+  set(FLUTTER_TARGET_PLATFORM "windows-x64")
+endif()
+
 # === Flutter Library ===
 set(FLUTTER_LIBRARY "${EPHEMERAL_DIR}/flutter_windows.dll")
 
@@ -92,7 +97,7 @@ add_custom_command(
   COMMAND ${CMAKE_COMMAND} -E env
     ${FLUTTER_TOOL_ENVIRONMENT}
     "${FLUTTER_ROOT}/packages/flutter_tools/bin/tool_backend.bat"
-      windows-x64 $<CONFIG>
+      ${FLUTTER_TARGET_PLATFORM} $<CONFIG>
   VERBATIM
 )
 add_custom_target(flutter_assemble DEPENDS

dev/benchmarks/complex_layout/windows/flutter/CMakeLists.txt

@@ -14,6 +14,11 @@ include(${EPHEMERAL_DIR}/generated_config.cmake)
 # https://github.com/flutter/flutter/issues/57146.
 set(WRAPPER_ROOT "${EPHEMERAL_DIR}/cpp_client_wrapper")
 
+# Set fallback configurations for older versions of the flutter tool.
+if (NOT DEFINED FLUTTER_TARGET_PLATFORM)
+  set(FLUTTER_TARGET_PLATFORM "windows-x64")
+endif()
+
 # === Flutter Library ===
 set(FLUTTER_LIBRARY "${EPHEMERAL_DIR}/flutter_windows.dll")
 
@@ -96,7 +101,7 @@ add_custom_command(
   COMMAND ${CMAKE_COMMAND} -E env
     ${FLUTTER_TOOL_ENVIRONMENT}
     "${FLUTTER_ROOT}/packages/flutter_tools/bin/tool_backend.bat"
-      windows-x64 $<CONFIG>
+      ${FLUTTER_TARGET_PLATFORM} $<CONFIG>
   VERBATIM
 )
 add_custom_target(flutter_assemble DEPENDS

dev/devicelab/lib/tasks/perf_tests.dart

@@ -894,6 +894,7 @@ class StartupTest {
             testDirectory,
             'build',
             'windows',
+            'x64',
             'runner',
             'Profile',
             '$basename.exe'
@@ -1645,6 +1646,7 @@ class CompileTest {
           cwd,
           'build',
           'windows',
+          'x64',
           'runner',
           'release',
           '$basename.exe');

dev/devicelab/lib/tasks/plugin_tests.dart

@@ -294,7 +294,7 @@ public class $pluginClass: NSObject, FlutterPlugin {
         }
       case 'windows':
         if (await exec(
-          path.join(rootPath, 'build', 'windows', 'plugins', 'plugintest', 'Release', 'plugintest_test.exe'),
+          path.join(rootPath, 'build', 'windows', 'x64', 'plugins', 'plugintest', 'Release', 'plugintest_test.exe'),
           <String>[],
           canFail: true,
         ) != 0) {

dev/devicelab/lib/tasks/run_tests.dart

@@ -178,7 +178,7 @@ class WindowsRunOutputTest extends DesktopRunOutputTest {
     multiLine: true,
   );
   static final RegExp _builtOutput = RegExp(
-    r'Built build\\windows\\runner\\(Debug|Release)\\\w+\.exe( \(\d+(\.\d+)?MB\))?\.',
+    r'Built build\\windows\\x64\\runner\\(Debug|Release)\\\w+\.exe( \(\d+(\.\d+)?MB\))?\.',
   );
 
   @override
@@ -205,7 +205,7 @@ class WindowsRunOutputTest extends DesktopRunOutputTest {
 
         return true;
       },
-      'Built build\\windows\\runner\\$buildMode\\app.exe',
+      'Built build\\windows\\x64\\runner\\$buildMode\\app.exe',
     );
   }
 }

dev/integration_tests/flutter_gallery/windows/flutter/CMakeLists.txt

@@ -1,3 +1,4 @@
+# This file controls Flutter-level build steps. It should not be edited.
 cmake_minimum_required(VERSION 3.14)
 
 set(EPHEMERAL_DIR "${CMAKE_CURRENT_SOURCE_DIR}/ephemeral")
@@ -9,6 +10,11 @@ include(${EPHEMERAL_DIR}/generated_config.cmake)
 # https://github.com/flutter/flutter/issues/57146.
 set(WRAPPER_ROOT "${EPHEMERAL_DIR}/cpp_client_wrapper")
 
+# Set fallback configurations for older versions of the flutter tool.
+if (NOT DEFINED FLUTTER_TARGET_PLATFORM)
+  set(FLUTTER_TARGET_PLATFORM "windows-x64")
+endif()
+
 # === Flutter Library ===
 set(FLUTTER_LIBRARY "${EPHEMERAL_DIR}/flutter_windows.dll")
 
@@ -91,7 +97,7 @@ add_custom_command(
   COMMAND ${CMAKE_COMMAND} -E env
     ${FLUTTER_TOOL_ENVIRONMENT}
     "${FLUTTER_ROOT}/packages/flutter_tools/bin/tool_backend.bat"
-      windows-x64 $<CONFIG>
+      ${FLUTTER_TARGET_PLATFORM} $<CONFIG>
   VERBATIM
 )
 add_custom_target(flutter_assemble DEPENDS

dev/integration_tests/ui/windows/flutter/CMakeLists.txt

@@ -10,6 +10,11 @@ include(${EPHEMERAL_DIR}/generated_config.cmake)
 # https://github.com/flutter/flutter/issues/57146.
 set(WRAPPER_ROOT "${EPHEMERAL_DIR}/cpp_client_wrapper")
 
+# Set fallback configurations for older versions of the flutter tool.
+if (NOT DEFINED FLUTTER_TARGET_PLATFORM)
+  set(FLUTTER_TARGET_PLATFORM "windows-x64")
+endif()
+
 # === Flutter Library ===
 set(FLUTTER_LIBRARY "${EPHEMERAL_DIR}/flutter_windows.dll")
 
@@ -92,7 +97,7 @@ add_custom_command(
   COMMAND ${CMAKE_COMMAND} -E env
     ${FLUTTER_TOOL_ENVIRONMENT}
     "${FLUTTER_ROOT}/packages/flutter_tools/bin/tool_backend.bat"
-      windows-x64 $<CONFIG>
+      ${FLUTTER_TARGET_PLATFORM} $<CONFIG>
   VERBATIM
 )
 add_custom_target(flutter_assemble DEPENDS

dev/integration_tests/windows_startup_test/windows/flutter/CMakeLists.txt

@@ -10,6 +10,11 @@ include(${EPHEMERAL_DIR}/generated_config.cmake)
 # https://github.com/flutter/flutter/issues/57146.
 set(WRAPPER_ROOT "${EPHEMERAL_DIR}/cpp_client_wrapper")
 
+# Set fallback configurations for older versions of the flutter tool.
+if (NOT DEFINED FLUTTER_TARGET_PLATFORM)
+  set(FLUTTER_TARGET_PLATFORM "windows-x64")
+endif()
+
 # === Flutter Library ===
 set(FLUTTER_LIBRARY "${EPHEMERAL_DIR}/flutter_windows.dll")
 
@@ -92,7 +97,7 @@ add_custom_command(
   COMMAND ${CMAKE_COMMAND} -E env
     ${FLUTTER_TOOL_ENVIRONMENT}
     "${FLUTTER_ROOT}/packages/flutter_tools/bin/tool_backend.bat"
-      windows-x64 $<CONFIG>
+      ${FLUTTER_TARGET_PLATFORM} $<CONFIG>
   VERBATIM
 )
 add_custom_target(flutter_assemble DEPENDS

dev/manual_tests/windows/flutter/CMakeLists.txt

@@ -1,3 +1,4 @@
+# This file controls Flutter-level build steps. It should not be edited.
 cmake_minimum_required(VERSION 3.14)
 
 set(EPHEMERAL_DIR "${CMAKE_CURRENT_SOURCE_DIR}/ephemeral")
@@ -9,6 +10,11 @@ include(${EPHEMERAL_DIR}/generated_config.cmake)
 # https://github.com/flutter/flutter/issues/57146.
 set(WRAPPER_ROOT "${EPHEMERAL_DIR}/cpp_client_wrapper")
 
+# Set fallback configurations for older versions of the flutter tool.
+if (NOT DEFINED FLUTTER_TARGET_PLATFORM)
+  set(FLUTTER_TARGET_PLATFORM "windows-x64")
+endif()
+
 # === Flutter Library ===
 set(FLUTTER_LIBRARY "${EPHEMERAL_DIR}/flutter_windows.dll")
 
@@ -91,7 +97,7 @@ add_custom_command(
   COMMAND ${CMAKE_COMMAND} -E env
     ${FLUTTER_TOOL_ENVIRONMENT}
     "${FLUTTER_ROOT}/packages/flutter_tools/bin/tool_backend.bat"
-      windows-x64 $<CONFIG>
+      ${FLUTTER_TARGET_PLATFORM} $<CONFIG>
   VERBATIM
 )
 add_custom_target(flutter_assemble DEPENDS

examples/api/windows/flutter/CMakeLists.txt

@@ -1,3 +1,4 @@
+# This file controls Flutter-level build steps. It should not be edited.
 cmake_minimum_required(VERSION 3.14)
 
 set(EPHEMERAL_DIR "${CMAKE_CURRENT_SOURCE_DIR}/ephemeral")
@@ -9,6 +10,11 @@ include(${EPHEMERAL_DIR}/generated_config.cmake)
 # https://github.com/flutter/flutter/issues/57146.
 set(WRAPPER_ROOT "${EPHEMERAL_DIR}/cpp_client_wrapper")
 
+# Set fallback configurations for older versions of the flutter tool.
+if (NOT DEFINED FLUTTER_TARGET_PLATFORM)
+  set(FLUTTER_TARGET_PLATFORM "windows-x64")
+endif()
+
 # === Flutter Library ===
 set(FLUTTER_LIBRARY "${EPHEMERAL_DIR}/flutter_windows.dll")
 
@@ -91,7 +97,7 @@ add_custom_command(
   COMMAND ${CMAKE_COMMAND} -E env
     ${FLUTTER_TOOL_ENVIRONMENT}
     "${FLUTTER_ROOT}/packages/flutter_tools/bin/tool_backend.bat"
-      windows-x64 $<CONFIG>
+      ${FLUTTER_TARGET_PLATFORM} $<CONFIG>
   VERBATIM
 )
 add_custom_target(flutter_assemble DEPENDS

examples/flutter_view/windows/flutter/CMakeLists.txt

@@ -14,6 +14,11 @@ include(${EPHEMERAL_DIR}/generated_config.cmake)
 # https://github.com/flutter/flutter/issues/57146.
 set(WRAPPER_ROOT "${EPHEMERAL_DIR}/cpp_client_wrapper")
 
+# Set fallback configurations for older versions of the flutter tool.
+if (NOT DEFINED FLUTTER_TARGET_PLATFORM)
+  set(FLUTTER_TARGET_PLATFORM "windows-x64")
+endif()
+
 # === Flutter Library ===
 set(FLUTTER_LIBRARY "${EPHEMERAL_DIR}/flutter_windows.dll")
 
@@ -96,7 +101,7 @@ add_custom_command(
   COMMAND ${CMAKE_COMMAND} -E env
     ${FLUTTER_TOOL_ENVIRONMENT}
     "${FLUTTER_ROOT}/packages/flutter_tools/bin/tool_backend.bat"
-      windows-x64 $<CONFIG>
+      ${FLUTTER_TARGET_PLATFORM} $<CONFIG>
   VERBATIM
 )
 add_custom_target(flutter_assemble DEPENDS

examples/hello_world/windows/flutter/CMakeLists.txt

@@ -10,6 +10,11 @@ include(${EPHEMERAL_DIR}/generated_config.cmake)
 # https://github.com/flutter/flutter/issues/57146.
 set(WRAPPER_ROOT "${EPHEMERAL_DIR}/cpp_client_wrapper")
 
+# Set fallback configurations for older versions of the flutter tool.
+if (NOT DEFINED FLUTTER_TARGET_PLATFORM)
+  set(FLUTTER_TARGET_PLATFORM "windows-x64")
+endif()
+
 # === Flutter Library ===
 set(FLUTTER_LIBRARY "${EPHEMERAL_DIR}/flutter_windows.dll")
 
@@ -92,7 +97,7 @@ add_custom_command(
   COMMAND ${CMAKE_COMMAND} -E env
     ${FLUTTER_TOOL_ENVIRONMENT}
     "${FLUTTER_ROOT}/packages/flutter_tools/bin/tool_backend.bat"
-      windows-x64 $<CONFIG>
+      ${FLUTTER_TARGET_PLATFORM} $<CONFIG>
   VERBATIM
 )
 add_custom_target(flutter_assemble DEPENDS

examples/layers/windows/flutter/CMakeLists.txt

@@ -10,6 +10,11 @@ include(${EPHEMERAL_DIR}/generated_config.cmake)
 # https://github.com/flutter/flutter/issues/57146.
 set(WRAPPER_ROOT "${EPHEMERAL_DIR}/cpp_client_wrapper")
 
+# Set fallback configurations for older versions of the flutter tool.
+if (NOT DEFINED FLUTTER_TARGET_PLATFORM)
+  set(FLUTTER_TARGET_PLATFORM "windows-x64")
+endif()
+
 # === Flutter Library ===
 set(FLUTTER_LIBRARY "${EPHEMERAL_DIR}/flutter_windows.dll")
 
@@ -92,7 +97,7 @@ add_custom_command(
   COMMAND ${CMAKE_COMMAND} -E env
     ${FLUTTER_TOOL_ENVIRONMENT}
     "${FLUTTER_ROOT}/packages/flutter_tools/bin/tool_backend.bat"
-      windows-x64 $<CONFIG>
+      ${FLUTTER_TARGET_PLATFORM} $<CONFIG>
   VERBATIM
 )
 add_custom_target(flutter_assemble DEPENDS

examples/platform_channel/windows/flutter/CMakeLists.txt

@@ -10,6 +10,11 @@ include(${EPHEMERAL_DIR}/generated_config.cmake)
 # https://github.com/flutter/flutter/issues/57146.
 set(WRAPPER_ROOT "${EPHEMERAL_DIR}/cpp_client_wrapper")
 
+# Set fallback configurations for older versions of the flutter tool.
+if (NOT DEFINED FLUTTER_TARGET_PLATFORM)
+  set(FLUTTER_TARGET_PLATFORM "windows-x64")
+endif()
+
 # === Flutter Library ===
 set(FLUTTER_LIBRARY "${EPHEMERAL_DIR}/flutter_windows.dll")
 
@@ -92,7 +97,7 @@ add_custom_command(
   COMMAND ${CMAKE_COMMAND} -E env
     ${FLUTTER_TOOL_ENVIRONMENT}
     "${FLUTTER_ROOT}/packages/flutter_tools/bin/tool_backend.bat"
-      windows-x64 $<CONFIG>
+      ${FLUTTER_TARGET_PLATFORM} $<CONFIG>
   VERBATIM
 )
 add_custom_target(flutter_assemble DEPENDS

examples/platform_view/windows/flutter/CMakeLists.txt

@@ -14,6 +14,11 @@ include(${EPHEMERAL_DIR}/generated_config.cmake)
 # https://github.com/flutter/flutter/issues/57146.
 set(WRAPPER_ROOT "${EPHEMERAL_DIR}/cpp_client_wrapper")
 
+# Set fallback configurations for older versions of the flutter tool.
+if (NOT DEFINED FLUTTER_TARGET_PLATFORM)
+  set(FLUTTER_TARGET_PLATFORM "windows-x64")
+endif()
+
 # === Flutter Library ===
 set(FLUTTER_LIBRARY "${EPHEMERAL_DIR}/flutter_windows.dll")
 
@@ -96,7 +101,7 @@ add_custom_command(
   COMMAND ${CMAKE_COMMAND} -E env
     ${FLUTTER_TOOL_ENVIRONMENT}
     "${FLUTTER_ROOT}/packages/flutter_tools/bin/tool_backend.bat"
-      windows-x64 $<CONFIG>
+      ${FLUTTER_TARGET_PLATFORM} $<CONFIG>
   VERBATIM
 )
 add_custom_target(flutter_assemble DEPENDS

packages/flutter_tools/lib/src/build_info.dart

@@ -872,8 +872,9 @@ String getLinuxBuildDirectory([TargetPlatform? targetPlatform]) {
 }
 
 /// Returns the Windows build output directory.
-String getWindowsBuildDirectory() {
+String getWindowsBuildDirectory(TargetPlatform targetPlatform) {
-  return globals.fs.path.join(getBuildDirectory(), 'windows');
+  final String arch = targetPlatform.simpleName;
+  return globals.fs.path.join(getBuildDirectory(), 'windows', arch);
 }
 
 /// Returns the Fuchsia build output directory.

packages/flutter_tools/lib/src/windows/application_package.dart

@@ -111,7 +111,7 @@ class BuildableWindowsApp extends WindowsApp {
   String executable(BuildMode buildMode) {
     final String? binaryName = getCmakeExecutableName(project);
     return globals.fs.path.join(
-        getWindowsBuildDirectory(),
+        getWindowsBuildDirectory(TargetPlatform.windows_x64),
         'runner',
         sentenceCase(buildMode.cliName),
         '$binaryName.exe',

packages/flutter_tools/lib/src/windows/build_windows.dart

@@ -18,6 +18,7 @@ import '../convert.dart';
 import '../flutter_plugins.dart';
 import '../globals.dart' as globals;
 import '../migrations/cmake_custom_command_migration.dart';
+import 'migrations/build_architecture_migration.dart';
 import 'migrations/show_window_migration.dart';
 import 'migrations/version_migration.dart';
 import 'visual_studio.dart';
@@ -52,10 +53,17 @@ Future<void> buildWindows(WindowsProject windowsProject, BuildInfo buildInfo, {
       'to learn about adding Windows support to a project.');
   }
 
+  // TODO(pbo-linaro): Add support for windows-arm64 platform, https://github.com/flutter/flutter/issues/129807
+  const TargetPlatform targetPlatform = TargetPlatform.windows_x64;
+  final Directory buildDirectory = globals.fs.directory(
+    getWindowsBuildDirectory(targetPlatform)
+  );
+
   final List<ProjectMigrator> migrators = <ProjectMigrator>[
     CmakeCustomCommandMigration(windowsProject, globals.logger),
     VersionMigration(windowsProject, globals.logger),
     ShowWindowMigration(windowsProject, globals.logger),
+    BuildArchitectureMigration(windowsProject, buildDirectory, globals.logger),
   ];
 
   final ProjectMigration migration = ProjectMigration(migrators);
@@ -79,7 +87,6 @@ Future<void> buildWindows(WindowsProject windowsProject, BuildInfo buildInfo, {
   }
 
   final String buildModeName = buildInfo.mode.cliName;
-  final Directory buildDirectory = globals.fs.directory(getWindowsBuildDirectory());
   final Status status = globals.logger.startProgress(
     'Building Windows application...',
   );
@@ -89,6 +96,7 @@ Future<void> buildWindows(WindowsProject windowsProject, BuildInfo buildInfo, {
       generator: cmakeGenerator,
       buildDir: buildDirectory,
       sourceDir: windowsProject.cmakeFile.parent,
+      targetPlatform: targetPlatform,
     );
     if (visualStudio.displayVersion == '17.1.0') {
       _fixBrokenCmakeGeneration(buildDirectory);
@@ -124,7 +132,11 @@ Future<void> buildWindows(WindowsProject windowsProject, BuildInfo buildInfo, {
       aotSnapshot: codeSizeFile,
       // This analysis is only supported for release builds.
       outputDirectory: globals.fs.directory(
-        globals.fs.path.join(getWindowsBuildDirectory(), 'runner', 'Release'),
+        globals.fs.path.join(
+          buildDirectory.path,
+          'runner',
+          'Release'
+        ),
       ),
       precompilerTrace: precompilerTrace,
       type: 'windows',
@@ -153,11 +165,18 @@ Future<void> _runCmakeGeneration({
   required String generator,
   required Directory buildDir,
   required Directory sourceDir,
+  required TargetPlatform targetPlatform,
 }) async {
+  if (targetPlatform != TargetPlatform.windows_x64) {
+    throwToolExit('Windows build supports only x64 target architecture');
+  }
+
   final Stopwatch sw = Stopwatch()..start();
 
   await buildDir.create(recursive: true);
   int result;
+  const String arch = 'x64';
+  const String flutterTargetPlatform = 'windows-x64';
   try {
     result = await globals.processUtils.stream(
       <String>[
@@ -168,6 +187,9 @@ Future<void> _runCmakeGeneration({
         buildDir.path,
         '-G',
         generator,
+        '-A',
+        arch,
+        '-DFLUTTER_TARGET_PLATFORM=$flutterTargetPlatform',
       ],
       trace: true,
     );

packages/flutter_tools/lib/src/windows/migrations/build_architecture_migration.dart

@@ -0,0 +1,126 @@
+// Copyright 2014 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import '../../base/file_system.dart';
+import '../../base/project_migrator.dart';
+import '../../cmake_project.dart';
+import 'utils.dart';
+
+const String _cmakeFileToolBackendBefore = r'''
+add_custom_command(
+  OUTPUT ${FLUTTER_LIBRARY} ${FLUTTER_LIBRARY_HEADERS}
+    ${CPP_WRAPPER_SOURCES_CORE} ${CPP_WRAPPER_SOURCES_PLUGIN}
+    ${CPP_WRAPPER_SOURCES_APP}
+    ${PHONY_OUTPUT}
+  COMMAND ${CMAKE_COMMAND} -E env
+    ${FLUTTER_TOOL_ENVIRONMENT}
+    "${FLUTTER_ROOT}/packages/flutter_tools/bin/tool_backend.bat"
+      windows-x64 $<CONFIG>
+  VERBATIM
+)
+''';
+
+const String _cmakeFileToolBackendAfter = r'''
+add_custom_command(
+  OUTPUT ${FLUTTER_LIBRARY} ${FLUTTER_LIBRARY_HEADERS}
+    ${CPP_WRAPPER_SOURCES_CORE} ${CPP_WRAPPER_SOURCES_PLUGIN}
+    ${CPP_WRAPPER_SOURCES_APP}
+    ${PHONY_OUTPUT}
+  COMMAND ${CMAKE_COMMAND} -E env
+    ${FLUTTER_TOOL_ENVIRONMENT}
+    "${FLUTTER_ROOT}/packages/flutter_tools/bin/tool_backend.bat"
+      ${FLUTTER_TARGET_PLATFORM} $<CONFIG>
+  VERBATIM
+)
+''';
+
+const String _cmakeFileTargetPlatformBefore = r'''
+# TODO: Move the rest of this into files in ephemeral. See
+# https://github.com/flutter/flutter/issues/57146.
+set(WRAPPER_ROOT "${EPHEMERAL_DIR}/cpp_client_wrapper")
+
+# === Flutter Library ===
+''';
+
+const String _cmakeFileTargetPlatformAfter = r'''
+# TODO: Move the rest of this into files in ephemeral. See
+# https://github.com/flutter/flutter/issues/57146.
+set(WRAPPER_ROOT "${EPHEMERAL_DIR}/cpp_client_wrapper")
+
+# Set fallback configurations for older versions of the flutter tool.
+if (NOT DEFINED FLUTTER_TARGET_PLATFORM)
+  set(FLUTTER_TARGET_PLATFORM "windows-x64")
+endif()
+
+# === Flutter Library ===
+''';
+
+/// Migrates Windows build to target specific architecture.
+/// In more, it deletes old runner folder
+class BuildArchitectureMigration extends ProjectMigrator {
+  BuildArchitectureMigration(
+    WindowsProject project,
+    Directory buildDirectory,
+    super.logger
+  )
+    : _cmakeFile = project.managedCmakeFile,
+      _buildDirectory = buildDirectory;
+
+  final File _cmakeFile;
+  final Directory _buildDirectory;
+
+  @override
+  void migrate() {
+    final Directory oldRunnerDirectory = _buildDirectory
+      .parent
+      .childDirectory('runner');
+    if (oldRunnerDirectory.existsSync()) {
+      logger.printTrace('''
+Deleting previous build folder ${oldRunnerDirectory.path}.
+New binaries can be found in ${_buildDirectory.childDirectory('runner').path}.
+''');
+      try {
+        oldRunnerDirectory.deleteSync(recursive: true);
+      } on FileSystemException catch (error) {
+        logger.printError(
+          'Failed to remove ${oldRunnerDirectory.path}: $error. '
+          'A program may still be using a file in the directory or the directory itself. '
+          'To find and stop such a program, see: '
+          'https://superuser.com/questions/1333118/cant-delete-empty-folder-because-it-is-used'
+        );
+      }
+    }
+
+    // Skip this migration if the affected file does not exist. This indicates
+    // the app has done non-trivial changes to its runner and this migration
+    // might not work as expected if applied.
+    if (!_cmakeFile.existsSync()) {
+      logger.printTrace('''
+windows/flutter/CMakeLists.txt file not found, skipping build architecture migration.
+
+This indicates non-trivial changes have been made to the "windows" folder.
+If needed, you can reset it by deleting the "windows" folder and then using the
+"flutter create --platforms=windows ." command.
+''');
+      return;
+    }
+
+    // Migrate the windows/flutter/CMakeLists.txt file.
+    final String originalCmakeContents = _cmakeFile.readAsStringSync();
+    final String cmakeContentsWithTargetPlatform = replaceFirst(
+      originalCmakeContents,
+      _cmakeFileTargetPlatformBefore,
+      _cmakeFileTargetPlatformAfter,
+    );
+    final String newCmakeContents = replaceFirst(
+      cmakeContentsWithTargetPlatform,
+      _cmakeFileToolBackendBefore,
+      _cmakeFileToolBackendAfter,
+    );
+    if (originalCmakeContents != newCmakeContents) {
+      logger.printStatus('windows/flutter/CMakeLists.txt does not use FLUTTER_TARGET_PLATFORM, updating.');
+      _cmakeFile.writeAsStringSync(newCmakeContents);
+    }
+  }
+}

packages/flutter_tools/templates/app_shared/windows.tmpl/flutter/CMakeLists.txt

@@ -10,6 +10,11 @@ include(${EPHEMERAL_DIR}/generated_config.cmake)
 # https://github.com/flutter/flutter/issues/57146.
 set(WRAPPER_ROOT "${EPHEMERAL_DIR}/cpp_client_wrapper")
 
+# Set fallback configurations for older versions of the flutter tool.
+if (NOT DEFINED FLUTTER_TARGET_PLATFORM)
+  set(FLUTTER_TARGET_PLATFORM "windows-x64")
+endif()
+
 # === Flutter Library ===
 set(FLUTTER_LIBRARY "${EPHEMERAL_DIR}/flutter_windows.dll")
 
@@ -92,7 +97,7 @@ add_custom_command(
   COMMAND ${CMAKE_COMMAND} -E env
     ${FLUTTER_TOOL_ENVIRONMENT}
     "${FLUTTER_ROOT}/packages/flutter_tools/bin/tool_backend.bat"
-      windows-x64 $<CONFIG>
+      ${FLUTTER_TARGET_PLATFORM} $<CONFIG>
   VERBATIM
 )
 add_custom_target(flutter_assemble DEPENDS

packages/flutter_tools/test/commands.shard/hermetic/build_windows_test.dart

@@ -82,9 +82,12 @@ void main() {
         '-S',
         fileSystem.path.absolute(fileSystem.path.dirname(buildFilePath)),
         '-B',
-        r'build\windows',
+        r'build\windows\x64',
         '-G',
         generator,
+        '-A',
+        'x64',
+        '-DFLUTTER_TARGET_PLATFORM=windows-x64',
       ],
       onRun: onRun,
     );
@@ -100,7 +103,7 @@ void main() {
       command: <String>[
         _cmakePath,
         '--build',
-        r'build\windows',
+        r'build\windows\x64',
         '--config',
         buildMode,
         ...<String>['--target', 'INSTALL'],
@@ -222,21 +225,21 @@ Microsoft (R) Build Engine version 16.6.0+5ff7b0c9e for .NET Framework
 Copyright (C) Microsoft Corporation. All rights reserved.
 
   Checking Build System
-  Generating C:/foo/windows/flutter/ephemeral/flutter_windows.dll, [etc], _phony_
+  Generating C:/foo/windows/x64/flutter/ephemeral/flutter_windows.dll, [etc], _phony_
-  Building Custom Rule C:/foo/windows/flutter/CMakeLists.txt
+  Building Custom Rule C:/foo/windows/x64/flutter/CMakeLists.txt
   standard_codec.cc
   Generating Code...
-  flutter_wrapper_plugin.vcxproj -> C:\foo\build\windows\flutter\Debug\flutter_wrapper_plugin.lib
+  flutter_wrapper_plugin.vcxproj -> C:\foo\build\windows\x64\flutter\Debug\flutter_wrapper_plugin.lib
-C:\foo\windows\runner\main.cpp(18): error C2220: the following warning is treated as an error [C:\foo\build\windows\runner\test.vcxproj]
+C:\foo\windows\x64\runner\main.cpp(18): error C2220: the following warning is treated as an error [C:\foo\build\windows\x64\runner\test.vcxproj]
-C:\foo\windows\runner\main.cpp(18): warning C4706: assignment within conditional expression [C:\foo\build\windows\runner\test.vcxproj]
+C:\foo\windows\x64\runner\main.cpp(18): warning C4706: assignment within conditional expression [C:\foo\build\windows\x64\runner\test.vcxproj]
-main.obj : error LNK2019: unresolved external symbol "void __cdecl Bar(void)" (?Bar@@YAXXZ) referenced in function wWinMain [C:\foo\build\windows\runner\test.vcxproj]
+main.obj : error LNK2019: unresolved external symbol "void __cdecl Bar(void)" (?Bar@@YAXXZ) referenced in function wWinMain [C:\foo\build\windows\x64\runner\test.vcxproj]
-C:\foo\build\windows\runner\Debug\test.exe : fatal error LNK1120: 1 unresolved externals [C:\foo\build\windows\runner\test.vcxproj]
+C:\foo\build\windows\x64\runner\Debug\test.exe : fatal error LNK1120: 1 unresolved externals [C:\foo\build\windows\x64\runner\test.vcxproj]
-  Building Custom Rule C:/foo/windows/runner/CMakeLists.txt
+  Building Custom Rule C:/foo/windows/x64/runner/CMakeLists.txt
   flutter_window.cpp
   main.cpp
-C:\foo\windows\runner\main.cpp(17,1): error C2065: 'Baz': undeclared identifier [C:\foo\build\windows\runner\test.vcxproj]
+C:\foo\windows\x64\runner\main.cpp(17,1): error C2065: 'Baz': undeclared identifier [C:\foo\build\windows\x64\runner\test.vcxproj]
   -- Install configuration: "Debug"
-  -- Installing: C:/foo/build/windows/runner/Debug/data/icudtl.dat
+  -- Installing: C:/foo/build/windows/x64/runner/Debug/data/icudtl.dat
 ''';
 
     processManager = FakeProcessManager.list(<FakeCommand>[
@@ -251,11 +254,11 @@ C:\foo\windows\runner\main.cpp(17,1): error C2065: 'Baz': undeclared identifier
     );
     // Just the warnings and errors should be surfaced.
     expect(testLogger.errorText, r'''
-C:\foo\windows\runner\main.cpp(18): error C2220: the following warning is treated as an error [C:\foo\build\windows\runner\test.vcxproj]
+C:\foo\windows\x64\runner\main.cpp(18): error C2220: the following warning is treated as an error [C:\foo\build\windows\x64\runner\test.vcxproj]
-C:\foo\windows\runner\main.cpp(18): warning C4706: assignment within conditional expression [C:\foo\build\windows\runner\test.vcxproj]
+C:\foo\windows\x64\runner\main.cpp(18): warning C4706: assignment within conditional expression [C:\foo\build\windows\x64\runner\test.vcxproj]
-main.obj : error LNK2019: unresolved external symbol "void __cdecl Bar(void)" (?Bar@@YAXXZ) referenced in function wWinMain [C:\foo\build\windows\runner\test.vcxproj]
+main.obj : error LNK2019: unresolved external symbol "void __cdecl Bar(void)" (?Bar@@YAXXZ) referenced in function wWinMain [C:\foo\build\windows\x64\runner\test.vcxproj]
-C:\foo\build\windows\runner\Debug\test.exe : fatal error LNK1120: 1 unresolved externals [C:\foo\build\windows\runner\test.vcxproj]
+C:\foo\build\windows\x64\runner\Debug\test.exe : fatal error LNK1120: 1 unresolved externals [C:\foo\build\windows\x64\runner\test.vcxproj]
-C:\foo\windows\runner\main.cpp(17,1): error C2065: 'Baz': undeclared identifier [C:\foo\build\windows\runner\test.vcxproj]
+C:\foo\windows\x64\runner\main.cpp(17,1): error C2065: 'Baz': undeclared identifier [C:\foo\build\windows\x64\runner\test.vcxproj]
 ''');
   }, overrides: <Type, Generator>{
     FileSystem: () => fileSystem,
@@ -311,7 +314,7 @@ C:\foo\windows\runner\main.cpp(17,1): error C2065: 'Baz': undeclared identifier
 <?xml version="1.0" encoding="utf-8"?>
 <Project DefaultTargets="Build" ToolsVersion="17.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <ItemGroup>
-    <CustomBuild Include="somepath\build\windows\CMakeFiles\8b570225f626c250e12bc1ede88babae\flutter_windows.dll.rule">
+    <CustomBuild Include="somepath\build\windows\x64\CMakeFiles\8b570225f626c250e12bc1ede88babae\flutter_windows.dll.rule">
       <Message Condition="'$(Configuration)|$(Platform)'=='Debug|x64'">Generating some files</Message>
       <Command Condition="'$(Configuration)|$(Platform)'=='Debug|x64'">setlocal
 "C:\Program Files\Microsoft Visual Studio\2022\Professional\Common7\IDE\CommonExtensions\Microsoft\CMake\CMake\bin\cmake.exe" -E env FOO=bar C:/src/flutter/packages/flutter_tools/bin/tool_backend.bat windows-x64 Debug
@@ -391,6 +394,7 @@ if %errorlevel% neq 0 goto :VCEnd</Command>
     final File assembleProject = fileSystem.currentDirectory
       .childDirectory('build')
       .childDirectory('windows')
+      .childDirectory('x64')
       .childDirectory('flutter')
       .childFile('flutter_assemble.vcxproj');
     assembleProject.createSync(recursive: true);
@@ -892,7 +896,7 @@ if %errorlevel% neq 0 goto :VCEnd</Command>
       ..visualStudioOverride = fakeVisualStudio;
     setUpMockProjectFilesForBuild();
 
-    fileSystem.file(r'build\windows\runner\Release\app.so')
+    fileSystem.file(r'build\windows\x64\runner\Release\app.so')
       ..createSync(recursive: true)
       ..writeAsBytesSync(List<int>.generate(10000, (int index) => 0));
 

packages/flutter_tools/test/general.shard/windows/migrations/build_architecture_migration_test.dart

@@ -0,0 +1,299 @@
+// Copyright 2014 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'package:file/file.dart';
+import 'package:file/memory.dart';
+import 'package:flutter_tools/src/base/logger.dart';
+import 'package:flutter_tools/src/base/terminal.dart';
+import 'package:flutter_tools/src/cmake_project.dart';
+import 'package:flutter_tools/src/windows/migrations/build_architecture_migration.dart';
+import 'package:test/fake.dart';
+
+import '../../../src/common.dart';
+
+void main () {
+  group('Windows Flutter build architecture migration', () {
+    late MemoryFileSystem memoryFileSystem;
+    late BufferLogger testLogger;
+    late FakeWindowsProject mockProject;
+    late File cmakeFile;
+    late Directory buildDirectory;
+
+    setUp(() {
+      memoryFileSystem = MemoryFileSystem.test();
+      cmakeFile = memoryFileSystem.file('CMakeLists.txt');
+      buildDirectory = memoryFileSystem.directory('x64');
+
+      testLogger = BufferLogger(
+        terminal: Terminal.test(),
+        outputPreferences: OutputPreferences.test(),
+      );
+
+      mockProject = FakeWindowsProject(cmakeFile);
+    });
+
+    testWithoutContext('delete old runner directory', () {
+      buildDirectory.createSync();
+      final Directory oldRunnerDirectory =
+        buildDirectory
+        .parent
+        .childDirectory('runner');
+      oldRunnerDirectory.createSync();
+      final File executable = oldRunnerDirectory.childFile('program.exe');
+      executable.createSync();
+      expect(oldRunnerDirectory.existsSync(), isTrue);
+
+      final BuildArchitectureMigration migration = BuildArchitectureMigration(
+        mockProject,
+        buildDirectory,
+        testLogger,
+      );
+      migration.migrate();
+
+      expect(oldRunnerDirectory.existsSync(), isFalse);
+      expect(testLogger.traceText,
+        contains(
+          'Deleting previous build folder ./runner.\n'
+          'New binaries can be found in x64/runner.\n'
+        )
+      );
+      expect(testLogger.statusText, isEmpty);
+    });
+
+    testWithoutContext('skipped if CMake file is missing', () {
+      final BuildArchitectureMigration migration = BuildArchitectureMigration(
+        mockProject,
+        buildDirectory,
+        testLogger,
+      );
+      migration.migrate();
+      expect(cmakeFile.existsSync(), isFalse);
+
+      expect(testLogger.traceText,
+        contains('windows/flutter/CMakeLists.txt file not found, skipping build architecture migration'));
+      expect(testLogger.statusText, isEmpty);
+    });
+
+    testWithoutContext('skipped if nothing to migrate', () {
+      const String cmakeFileContents = 'Nothing to migrate';
+
+      cmakeFile.writeAsStringSync(cmakeFileContents);
+
+      final DateTime cmakeUpdatedAt = cmakeFile.lastModifiedSync();
+
+      final BuildArchitectureMigration buildArchitectureMigration = BuildArchitectureMigration(
+        mockProject,
+        buildDirectory,
+        testLogger,
+      );
+      buildArchitectureMigration.migrate();
+
+      expect(cmakeFile.lastModifiedSync(), cmakeUpdatedAt);
+      expect(cmakeFile.readAsStringSync(), cmakeFileContents);
+      expect(testLogger.statusText, isEmpty);
+    });
+
+    testWithoutContext('skipped if already migrated', () {
+      const String cmakeFileContents =
+        '# TODO: Move the rest of this into files in ephemeral. See\n'
+        '# https://github.com/flutter/flutter/issues/57146.\n'
+        'set(WRAPPER_ROOT "\${EPHEMERAL_DIR}/cpp_client_wrapper")\n'
+        '\n'
+        '# Set fallback configurations for older versions of the flutter tool.\n'
+        'if (NOT DEFINED FLUTTER_TARGET_PLATFORM)\n'
+        '  set(FLUTTER_TARGET_PLATFORM "windows-x64")\n'
+        'endif()\n'
+        '\n'
+        '# === Flutter Library ===\n'
+        '...\n'
+        'add_custom_command(\n'
+        '  OUTPUT \${FLUTTER_LIBRARY} \${FLUTTER_LIBRARY_HEADERS}\n'
+        '    \${CPP_WRAPPER_SOURCES_CORE} \${CPP_WRAPPER_SOURCES_PLUGIN}\n'
+        '    \${CPP_WRAPPER_SOURCES_APP}\n'
+        '    \${PHONY_OUTPUT}\n'
+        '  COMMAND \${CMAKE_COMMAND} -E env\n'
+        '    \${FLUTTER_TOOL_ENVIRONMENT}\n'
+        '    "\${FLUTTER_ROOT}/packages/flutter_tools/bin/tool_backend.bat"\n'
+        '      \${FLUTTER_TARGET_PLATFORM} \$<CONFIG>\n'
+        '  VERBATIM\n'
+        ')\n';
+
+      cmakeFile.writeAsStringSync(cmakeFileContents);
+
+      final DateTime cmakeUpdatedAt = cmakeFile.lastModifiedSync();
+
+      final BuildArchitectureMigration buildArchitectureMigration = BuildArchitectureMigration(
+        mockProject,
+        buildDirectory,
+        testLogger,
+      );
+      buildArchitectureMigration.migrate();
+
+      expect(cmakeFile.lastModifiedSync(), cmakeUpdatedAt);
+      expect(cmakeFile.readAsStringSync(), cmakeFileContents);
+
+      expect(testLogger.statusText, isEmpty);
+    });
+
+    testWithoutContext('skipped if already migrated (CRLF)', () {
+      const String cmakeFileContents =
+        '# TODO: Move the rest of this into files in ephemeral. See\r\n'
+        '# https://github.com/flutter/flutter/issues/57146.\r\n'
+        'set(WRAPPER_ROOT "\${EPHEMERAL_DIR}/cpp_client_wrapper")\r\n'
+        '\r\n'
+        '# Set fallback configurations for older versions of the flutter tool.\r\n'
+        'if (NOT DEFINED FLUTTER_TARGET_PLATFORM)\r\n'
+        '  set(FLUTTER_TARGET_PLATFORM "windows-x64")\r\n'
+        'endif()\r\n'
+        '\r\n'
+        '# === Flutter Library ===\r\n'
+        '...\r\n'
+        'add_custom_command(\r\n'
+        '  OUTPUT \${FLUTTER_LIBRARY} \${FLUTTER_LIBRARY_HEADERS}\r\n'
+        '    \${CPP_WRAPPER_SOURCES_CORE} \${CPP_WRAPPER_SOURCES_PLUGIN}\r\n'
+        '    \${CPP_WRAPPER_SOURCES_APP}\r\n'
+        '    \${PHONY_OUTPUT}\r\n'
+        '  COMMAND \${CMAKE_COMMAND} -E env\r\n'
+        '    \${FLUTTER_TOOL_ENVIRONMENT}\r\n'
+        '    "\${FLUTTER_ROOT}/packages/flutter_tools/bin/tool_backend.bat"\r\n'
+        '      \${FLUTTER_TARGET_PLATFORM} \$<CONFIG>\r\n'
+        '  VERBATIM\r\n'
+        ')\r\n';
+
+      cmakeFile.writeAsStringSync(cmakeFileContents);
+
+      final DateTime cmakeUpdatedAt = cmakeFile.lastModifiedSync();
+
+      final BuildArchitectureMigration buildArchitectureMigration = BuildArchitectureMigration(
+        mockProject,
+        buildDirectory,
+        testLogger,
+      );
+      buildArchitectureMigration.migrate();
+
+      expect(cmakeFile.lastModifiedSync(), cmakeUpdatedAt);
+      expect(cmakeFile.readAsStringSync(), cmakeFileContents);
+
+      expect(testLogger.statusText, isEmpty);
+    });
+
+    testWithoutContext('migrates project to set the target platform', () {
+      cmakeFile.writeAsStringSync(
+        '# TODO: Move the rest of this into files in ephemeral. See\n'
+        '# https://github.com/flutter/flutter/issues/57146.\n'
+        'set(WRAPPER_ROOT "\${EPHEMERAL_DIR}/cpp_client_wrapper")\n'
+        '\n'
+        '# === Flutter Library ===\n'
+        '...\n'
+        'add_custom_command(\n'
+        '  OUTPUT \${FLUTTER_LIBRARY} \${FLUTTER_LIBRARY_HEADERS}\n'
+        '    \${CPP_WRAPPER_SOURCES_CORE} \${CPP_WRAPPER_SOURCES_PLUGIN}\n'
+        '    \${CPP_WRAPPER_SOURCES_APP}\n'
+        '    \${PHONY_OUTPUT}\n'
+        '  COMMAND \${CMAKE_COMMAND} -E env\n'
+        '    \${FLUTTER_TOOL_ENVIRONMENT}\n'
+        '    "\${FLUTTER_ROOT}/packages/flutter_tools/bin/tool_backend.bat"\n'
+        '      windows-x64 \$<CONFIG>\n'
+        '  VERBATIM\n'
+        ')\n'
+      );
+      final BuildArchitectureMigration buildArchitectureMigration = BuildArchitectureMigration(
+        mockProject,
+        buildDirectory,
+        testLogger,
+      );
+      buildArchitectureMigration.migrate();
+
+      expect(cmakeFile.readAsStringSync(),
+        '# TODO: Move the rest of this into files in ephemeral. See\n'
+        '# https://github.com/flutter/flutter/issues/57146.\n'
+        'set(WRAPPER_ROOT "\${EPHEMERAL_DIR}/cpp_client_wrapper")\n'
+        '\n'
+        '# Set fallback configurations for older versions of the flutter tool.\n'
+        'if (NOT DEFINED FLUTTER_TARGET_PLATFORM)\n'
+        '  set(FLUTTER_TARGET_PLATFORM "windows-x64")\n'
+        'endif()\n'
+        '\n'
+        '# === Flutter Library ===\n'
+        '...\n'
+        'add_custom_command(\n'
+        '  OUTPUT \${FLUTTER_LIBRARY} \${FLUTTER_LIBRARY_HEADERS}\n'
+        '    \${CPP_WRAPPER_SOURCES_CORE} \${CPP_WRAPPER_SOURCES_PLUGIN}\n'
+        '    \${CPP_WRAPPER_SOURCES_APP}\n'
+        '    \${PHONY_OUTPUT}\n'
+        '  COMMAND \${CMAKE_COMMAND} -E env\n'
+        '    \${FLUTTER_TOOL_ENVIRONMENT}\n'
+        '    "\${FLUTTER_ROOT}/packages/flutter_tools/bin/tool_backend.bat"\n'
+        '      \${FLUTTER_TARGET_PLATFORM} \$<CONFIG>\n'
+        '  VERBATIM\n'
+        ')\n'
+      );
+
+      expect(testLogger.statusText, contains('windows/flutter/CMakeLists.txt does not use FLUTTER_TARGET_PLATFORM, updating.'));
+    });
+
+    testWithoutContext('migrates project to set the target platform (CRLF)', () {
+      cmakeFile.writeAsStringSync(
+        '# TODO: Move the rest of this into files in ephemeral. See\r\n'
+        '# https://github.com/flutter/flutter/issues/57146.\r\n'
+        'set(WRAPPER_ROOT "\${EPHEMERAL_DIR}/cpp_client_wrapper")\r\n'
+        '\r\n'
+        '# === Flutter Library ===\r\n'
+        '...\r\n'
+        'add_custom_command(\r\n'
+        '  OUTPUT \${FLUTTER_LIBRARY} \${FLUTTER_LIBRARY_HEADERS}\r\n'
+        '    \${CPP_WRAPPER_SOURCES_CORE} \${CPP_WRAPPER_SOURCES_PLUGIN}\r\n'
+        '    \${CPP_WRAPPER_SOURCES_APP}\r\n'
+        '    \${PHONY_OUTPUT}\r\n'
+        '  COMMAND \${CMAKE_COMMAND} -E env\r\n'
+        '    \${FLUTTER_TOOL_ENVIRONMENT}\r\n'
+        '    "\${FLUTTER_ROOT}/packages/flutter_tools/bin/tool_backend.bat"\r\n'
+        '      windows-x64 \$<CONFIG>\r\n'
+        '  VERBATIM\r\n'
+        ')\r\n'
+      );
+
+      final BuildArchitectureMigration buildArchitectureMigration = BuildArchitectureMigration(
+        mockProject,
+        buildDirectory,
+        testLogger,
+      );
+      buildArchitectureMigration.migrate();
+
+      expect(cmakeFile.readAsStringSync(),
+        '# TODO: Move the rest of this into files in ephemeral. See\r\n'
+        '# https://github.com/flutter/flutter/issues/57146.\r\n'
+        'set(WRAPPER_ROOT "\${EPHEMERAL_DIR}/cpp_client_wrapper")\r\n'
+        '\r\n'
+        '# Set fallback configurations for older versions of the flutter tool.\r\n'
+        'if (NOT DEFINED FLUTTER_TARGET_PLATFORM)\r\n'
+        '  set(FLUTTER_TARGET_PLATFORM "windows-x64")\r\n'
+        'endif()\r\n'
+        '\r\n'
+        '# === Flutter Library ===\r\n'
+        '...\r\n'
+        'add_custom_command(\r\n'
+        '  OUTPUT \${FLUTTER_LIBRARY} \${FLUTTER_LIBRARY_HEADERS}\r\n'
+        '    \${CPP_WRAPPER_SOURCES_CORE} \${CPP_WRAPPER_SOURCES_PLUGIN}\r\n'
+        '    \${CPP_WRAPPER_SOURCES_APP}\r\n'
+        '    \${PHONY_OUTPUT}\r\n'
+        '  COMMAND \${CMAKE_COMMAND} -E env\r\n'
+        '    \${FLUTTER_TOOL_ENVIRONMENT}\r\n'
+        '    "\${FLUTTER_ROOT}/packages/flutter_tools/bin/tool_backend.bat"\r\n'
+        '      \${FLUTTER_TARGET_PLATFORM} \$<CONFIG>\r\n'
+        '  VERBATIM\r\n'
+        ')\r\n'
+      );
+
+      expect(testLogger.statusText, contains('windows/flutter/CMakeLists.txt does not use FLUTTER_TARGET_PLATFORM, updating.'));
+    });
+  });
+}
+
+class FakeWindowsProject extends Fake implements WindowsProject {
+  FakeWindowsProject(this.managedCmakeFile);
+
+  @override
+  final File managedCmakeFile;
+}

packages/flutter_tools/test/integration.shard/flutter_build_windows_test.dart

@@ -45,6 +45,7 @@ void main() {
         projectRoot.path,
         'build',
         'windows',
+        'x64',
         'runner',
         'Release',
       ));