6f71aa9901
Towards https://github.com/flutter/flutter/issues/164315. This PR just writes `bin/cache/engine.stamp` identically to how `bin/internal/engine.version` would otherwise be written, with a caveat that _if_ `engine.version` is tracked, it is now _copied_ to `bin/cache/engine.stamp`. After this lands, I'll send PRs to update tooling that looks for `engine.version` and give a heads up to the larger team (i.e. Dart HH bot or whomever we will break by doing this).
Flutter SDK dependency versions
The files in this directory specifies pinned versions of various dependencies of the flutter SDK.
The bin/internal/engine.version file controls where to find compiled artifacts
of the engine. These artifacts are compiled in the Merge Queue for every commit
in the flutter repository.
The bin/internal/flutter_packages.version file specifies the version
of the flutter/packages repository to be used for testing. The
flutter/packages repository isn't an upstream dependency of
flutter/flutter; it is only used as part of the test suite for
verification, and the pinned version here makes sure that tests are
deterministic at each flutter/flutter commit.