Support for FFI calls with `@Native external` functions through Native assets on Windows. This enables bundling native code without any build-system boilerplate code.
For more info see:
* https://github.com/flutter/flutter/issues/129757
### Implementation details for Windows.
Mainly follows the design of https://github.com/flutter/flutter/pull/134031.
Specifically for Windows in this PR is the logic for finding the compiler `cl.exe` and environment variables that contain the paths to the Windows headers `vcvars.bat` based on `vswhere.exe`.
Reland of #134031. (Reverted in #135069.) Contains the fix for b/301051367 together with cl/567233346.
Support for FFI calls with `@Native external` functions through Native assets on Linux. This enables bundling native code without any build-system boilerplate code.
For more info see:
* https://github.com/flutter/flutter/issues/129757
### Implementation details for Linux.
Mainly follows the design of https://github.com/flutter/flutter/pull/130494.
Some differences are:
* Linux does not support cross compiling or compiling for multiple architectures, so this has not been implemented.
* Linux has no add2app.
The assets copying is done in the install-phase of the CMake build of a flutter app.
CMake requires the native assets folder to exist, so we create it also when the feature is disabled or there are no assets.
### Tests
This PR adds new tests to cover the various use cases.
* packages/flutter_tools/test/general.shard/linux/native_assets_test.dart
* Unit tests the Linux-specific part of building native assets.
It also extends various existing tests:
* packages/flutter_tools/test/integration.shard/native_assets_test.dart
* Runs (incl hot reload/hot restart), builds, builds frameworks for Linux and flutter-tester.
Reverts flutter/flutter#134031
context: b/301051367
Looked at the error message from the broken TAP target, but seems like the failure might be non trivial to resolve. Would it be okay if we revert this for now while it is being triaged?
Support for FFI calls with `@Native external` functions through Native assets on Linux. This enables bundling native code without any build-system boilerplate code.
For more info see:
* https://github.com/flutter/flutter/issues/129757
### Implementation details for Linux.
Mainly follows the design of https://github.com/flutter/flutter/pull/130494.
Some differences are:
* Linux does not support cross compiling or compiling for multiple architectures, so this has not been implemented.
* Linux has no add2app.
The assets copying is done in the install-phase of the CMake build of a flutter app.
CMake requires the native assets folder to exist, so we create it also when the feature is disabled or there are no assets.
### Tests
This PR adds new tests to cover the various use cases.
* packages/flutter_tools/test/general.shard/linux/native_assets_test.dart
* Unit tests the Linux-specific part of building native assets.
It also extends various existing tests:
* packages/flutter_tools/test/integration.shard/native_assets_test.dart
* Runs (incl hot reload/hot restart), builds, builds frameworks for Linux and flutter-tester.
