Fix the local-only lint errors due to an unexpected GeneratedPluginRegistrant.java

[matanlurey]

Remove android/**/GeneratedPluginRegistrant.java from the global .gitignore.

This file should never exist in the source tree, locally or on CI, and it existing/being hidden causes lint errors.

Background

Here is what we think happens:

• Someone opens $ENGINE/src/flutter/testing/scenario_app in VS Code
• VS Code picks this up as a "Flutter package", running flutter packages get
• The Flutter tool generates ../GeneratedPluginRegistrant.java, thinking this is a Flutter app
• The lint error fails on GeneratedPluginRegistrant

$ ninja -j100 -C out/android_debug_unopt_arm64/
FAILED: scenario_app/reports/lint-results.xml 
vpython3 ../../flutter/testing/rules/run_gradle.py /Users/aaclarke/dev/engine/src/flutter/testing/scenario_app/android lint --no-daemon -Pflutter_jar=/Users/aaclarke/dev/engine/src/out/android_debug_unopt_arm64/flutter.jar -Pout_dir=/Users/aaclarke/dev/engine/src/out/android_debug_unopt_arm64/scenario_app --project-cache-dir=/Users/aaclarke/dev/engine/src/out/android_debug_unopt_arm64/scenario_app/.gradle --gradle-user-home=/Users/aaclarke/dev/engine/src/out/android_debug_unopt_arm64/scenario_app/.gradle

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':app:lintDebug'.
>                 Lint found errors in the project; aborting build.
  
                  Fix the issues identified by lint, or create a baseline to see only new errors:
                  '''
                  android {
                      lint {
                          baseline = file("lint-baseline.xml")
                      }
                  }
                  '''
  
                  For more details, see https://developer.android.com/studio/write/lint#snapshot
  
                  Lint found 1 errors, 0 warnings. First failure:

/cc @christopherfujino for any other theories.

[reidbaker]

I dont think we want to remove this from gitignore. If there is a GeneratedPluginRegistrant.java then it should not be checked in. I think a better solution would be to modify the version of clean for whatever the engine build system uses to delete that class of file.

[matanlurey]

I dont think we want to remove this from gitignore. If there is a GeneratedPluginRegistrant.java then it should not be checked in. I think a better solution would be to modify the version of clean for whatever the engine build system uses to delete that class of file.

This is intentional, as gitignore hides the fact this file should not ever exist.

It's not a matter of not wanting to be checked-in, it's literally an invalid file in the engine repository.

[auto-submit]

auto label is removed for flutter/engine/50795, due to - The status or check suite Linux Framework Smoke Tests has failed. Please fix the issues identified (or deflake) before re-applying this label.

[jonahwilliams]

LGTM