Status: WIP. There are enough PRs out right now where I'm focusing on getting them landed/sticking before moving forward.

This is a follow-up to #132180 (comment).

As of #132180, --local-engine-host is optional, and if omitted, falls back to trying to derive the host.

We'd like to make this explicit instead, so:

• Announce the changes to the flutter tool to appropriate channels and wait a reasonable duration for feedback
• Update the devicelab.
  • PR: Update dev/devicelab/** to provide --local-engine-host. #132342
• Update the glfw examples and related examples in examples/*gl*/**.
  • PR: Update examples/** to provide --local-engine-host. engine#44610
• Update the tool_backend.dart and related scripts in flutter_tools/bin/*.
  • PR: Update flutter_tools/bin/*.(dart|sh) to provide, if set, --local-engine-host. #132336
• Update flutter.groovy and related.
  • PR: Update flutter_tools internals related to Gradle/XCode to set --local-engine-host. #132346
• Update the dart_roll_helper.py.
  • PR: Update dart_roller_helper.py to explicitly pass --local-engine-host to the flutter tool. buildroot#751
• Update the web engine web_ui/dev/build.dart and related files in web_ui/dev/*.
  • PR: Update web_ui/** to explicitly pass --local-engine-host to the flutter tool. engine#44613
• Update flutter_gbd.
  • Doesn't appear to need any changes, uses the device engine only.
• Update dev/bots/test.dart.
  • PR: Update dev/bots/test.dart (and friends) to provide --local-engine-host. #132354
• Update build_linux.dart.
  • PR: Add support for LOCAL_ENGINE_HOST to Linux/Mac/Win builds. #132579
• Update xcode_build_settings.dart.
  • PR: Add support for LOCAL_ENGINE_HOST to Linux/Mac/Win builds. #132579
• Update build_windows.dart.
  • PR: Add support for LOCAL_ENGINE_HOST to Linux/Mac/Win builds. #132579
• Try a CI run where --local-engine-host is required, and fix CI bots, tests, and bash scripts that aren't using it
  • PR: Treat missing --local-engine-host as fatal on CI-like systems. #132707
• Replace the warning message with throwToolExit and delete _getHostEngineBasename and friends