[fuchsia] enable assets_unittests (#164019)

It is an easy fix.

http://b/394632376

## Pre-launch Checklist

- [x] I read the [Contributor Guide] and followed the process outlined
there for submitting PRs.
- [x] I read the [Tree Hygiene] wiki page, which explains my
responsibilities.
- [x] I read and followed the [Flutter Style Guide], including [Features
we expect every widget to implement].
- [x] I signed the [CLA].
- [x] I listed at least one issue that this PR fixes in the description
above.
- [x] I updated/added relevant documentation (doc comments with `///`).
- [x] I added new tests to check the change I am making, or this PR is
[test-exempt].
- [x] I followed the [breaking change policy] and added [Data Driven
Fixes] where supported.
- [x] All existing and new tests are passing.

If you need help, consider asking for advice on the #hackers-new channel
on [Discord].

<!-- Links -->
[Contributor Guide]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#overview
[Tree Hygiene]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md
[test-exempt]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#tests
[Flutter Style Guide]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Style-guide-for-Flutter-repo.md
[Features we expect every widget to implement]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Style-guide-for-Flutter-repo.md#features-we-expect-every-widget-to-implement
[CLA]: https://cla.developers.google.com/
[flutter/tests]: https://github.com/flutter/tests
[breaking change policy]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#handling-breaking-changes
[Discord]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Chat.md
[Data Driven Fixes]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Data-driven-Fixes.md

engine/src/flutter/assets/native_assets_unittests.cc

@@ -32,6 +32,18 @@ const char* kTestManifest = R"({
                 "libmy_package.so"
             ]
         },
+        "fuchsia_arm64": {
+            "package:my_package/my_package_bindings_generated.dart": [
+                "absolute",
+                "libmy_package.so"
+            ]
+        },
+        "fuchsia_x64": {
+            "package:my_package/my_package_bindings_generated.dart": [
+                "absolute",
+                "libmy_package.so"
+            ]
+        },
         "macos_arm64": {
             "package:my_package/my_package_bindings_generated.dart": [
                 "absolute",
@@ -75,7 +87,7 @@ TEST(NativeAssetsManagerTest, NativeAssetsManifestParsing) {
   ASSERT_EQ(existing_asset[0], "absolute");
 #if defined(FML_OS_MACOSX)
   ASSERT_EQ(existing_asset[1], "my_package.framework/my_package");
-#elif defined(FML_OS_LINUX)
+#elif defined(FML_OS_LINUX) || defined(FML_OS_FUCHSIA)
   ASSERT_EQ(existing_asset[1], "libmy_package.so");
 #elif defined(FML_OS_WIN)
   ASSERT_EQ(existing_asset[1], "my_package.dll");

engine/src/flutter/testing/fuchsia/test_suites.yaml

@@ -6,9 +6,7 @@
 # Please keep the list alphabetical order.
 
 - test_command: test run fuchsia-pkg://fuchsia.com/assets_unittests#meta/assets_unittests.cm
-  disabled: flutter/engine/src/flutter/assets/native_assets_unittests.cc does not support fuchsia yet.
   package: assets_unittests-0.far
-  variant: disabled
 - test_command: test run fuchsia-pkg://fuchsia.com/client_wrapper_unittests#meta/client_wrapper_unittests.cm
   package: client_wrapper_unittests-0.far
 - test_command: test run fuchsia-pkg://fuchsia.com/common_cpp_core_unittests#meta/common_cpp_core_unittests.cm