Introduce architecture subdirectory for Windows build (#129805, #116196)

[pbo-linaro]

To implement windows-arm64 support, it is needed to add architecture as a subdirectory (#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.

The old "runner" folder is automatically cleaned to prevent confusion for users not aware of this change, and who could continue to use outdated binaries accidentally.

We didn't introduce any change in ephemeral build folder. This might be required when introducing another architecture, but it won't be a breaking change, as those files are not used by end user.

Since we use a fresh cmake folder, we introduce FLUTTER_TARGET_PLATFORM in flutter cmake file (#116196). This will be needed when targeting another architecture than x64, and will avoid to have to clean existing cmake files. An automatic migration was implemented to automate this change in existing applications.

Finally, we set a specific architecture when calling cmake. This fixes existing build and tests on Windows on Arm, where cmake tries to compile native windows-arm64 binaries by default (which fails to link x64 libraries). In more, it will avoid need to clean existing cmake files when introducing another architecture.

Design doc: flutter.dev/go/windows-arm64

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• I listed at least one issue that this PR fixes in the description above.
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• I added new tests to check the change I am making, or this PR is test-exempt.
• All existing and new tests are passing.

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[pbo-linaro]

@loic-sharma Here it is!
Your comments are welcome, and those from other flutter devs as well.

For now, I focused on a minimal change, with tests working (on x64 and arm64).
Probably I can update some documentation as well, don't hesitate to say.

[pbo-linaro]

Fixed error reported by flutter analyze.

[pbo-linaro]

Fixed license message.

[pbo-linaro]

@loic-sharma I'm not sure if the failure (windows plugin_test) means that there is something missing, or if the test script itself (located elsewhere?) should be updated to reflect new path to binary plugintest_test.exe.

If you could help on this, that would be nice :).

[andrewkolos]

@loic-sharma Would you be interested in reviewing this?

[loic-sharma]

Yup will do!

[loic-sharma]

Can we move this to the generated configs in _writeGeneratedFlutterConfig?

flutter/packages/flutter_tools/lib/src/cmake.dart

Lines 101 to 109 in b7acafa

	# Generated code do not commit.
	file(TO_CMAKE_PATH "$escapedFlutterRoot" FLUTTER_ROOT)
	file(TO_CMAKE_PATH "$escapedProjectDir" PROJECT_DIR)
	set(FLUTTER_VERSION "$version" PARENT_SCOPE)
	set(FLUTTER_VERSION_MAJOR ${version.major} PARENT_SCOPE)
	set(FLUTTER_VERSION_MINOR ${version.minor} PARENT_SCOPE)
	set(FLUTTER_VERSION_PATCH ${version.patch} PARENT_SCOPE)
	set(FLUTTER_VERSION_BUILD ${buildVersion ?? 0} PARENT_SCOPE)

[pbo-linaro]

Linux build adds it directly to the cmake command, and IMHO, it's more explicit that putting it in another function.
FLUTTER_VERSION_* stuff is the same for all architecture, thus it makes sense to factorize it in a single place.

What do you think?

[loic-sharma]

Hm I agree we should align with Linux. If we move FLUTTER_TARGET_PLATFORM to the generated CMake config file, we would need to also update Linux. That seems out-of-scope for this PR, and we can follow-up with this change later if needed.

That said, I'm curious as to why Linux chose this approach. The generated cmake config file makes it easier to use the CMake project without the Flutter tool. Regardless, I'll close this off!

[pbo-linaro]

Thanks for accepting this.

[christopherfujino]

What happens if someone directly invokes a build via cmake without providing -DFLUTTER_TARGET_PLATFORM?

[loic-sharma]

@loic-sharma I'm not sure if the failure (windows plugin_test) means that there is something missing, or if the test script itself (located elsewhere?) should be updated to reflect new path to binary plugintest_test.exe.

It looks like you'll need to update this:

flutter/dev/devicelab/lib/tasks/plugin_tests.dart

Lines 296 to 300 in 53082f6

	if (await exec(
	path.join(rootPath, 'build', 'windows', 'plugins', 'plugintest', 'Release', 'plugintest_test.exe'),
	<String>[],
	canFail: true,
	) != 0) {

You should be able to run this test locally using these instructions: https://github.com/flutter/flutter/tree/master/dev/devicelab#running-tests-locally

TLDR, this should work:

cd path/to/flutter
cd dev/devicelab
../../bin/cache/dart-sdk/bin/dart bin/test_runner.dart test -t plugin_test_windows

Let me know if you run into any problems!

[pbo-linaro]

First fixing failed test, before addressing other comments in review.

[pbo-linaro]

Pushed resolved changes.

[pbo-linaro]

Fixed analyze not happy with raw cmake strings 'if(...'.

[pbo-linaro]

Added change to hardcode TargetPlatform to getWindowsBuildDirectory.