This contains a fix needed to build with the latest Clang toolchain.

This eliminates use of third_party/gyp.

[Re-land] Add SPIR-V FragmentShader API to painting.dart

- Add a SPIR-V FragmentShader interface in painting.dart
- Create end to end pixel tests for ops supported by the SPIR-V to SkSL transpiler
- The end to end tests also test the c++ fragment shader implementation
Co-authored-by: NChristopher Crawford <chriscraws@gmail.com>

The gradle/android tooling will validate that ANDROID_HOME and
ANDROID_SDK_ROOT are precisely the same. So if they point to the same
directory but are not normalized this check will fail.

Fixes Dart-Flutter Head-Head-Head bot which failed with
```
Several environment variables and/or system properties contain different paths to the SDK.
  Please correct and use only one way to inject the SDK location.
  
  ANDROID_HOME: /b/s/w/ir/cache/builder/engine/src/flutter/testing/rules/../../../third_party/android_tools/sdk
  ANDROID_SDK_ROOT: /b/s/w/ir/cache/builder/engine/src/third_party/android_tools/sdk
```

This reverts commit a116cc0d.

This reverts commit 19f639db.

This reverts commit 14e27f9a.

This reverts commit 6d6ce343.

This is to minimize the number of environment variables being passed to
scripts from recipes.