Distribute macOS engine as an xcframework

[vashworth]

For Swift Package Manager to work with macOS, the macOS engine artifact needs to be an xcframework.

• [engine] Create FlutterMacOS.xcframework and archive it: Build macOS engine as an xcframework engine#50300
• [tool] Replace usage of FlutterMacOS.framework artifact with new FlutterMacOS.xcframework artifact
  • Ensure codesigning: Add FlutterMacOS.xcframework artifact #143244
• [tool] Stop building the xcframework on flutter build macos-framework and instead use the one in the artifact cache: Add FlutterMacOS.xcframework artifact #143244
• [engine] Remove FlutterMacOS.framework archive
  • Before the old FlutterMacOS.framework can be removed, we'll need to let the Flutter release team know so they can update their roll scripts, and coordinate with the Fl@G team to make sure build rules are updated, if needed.

Example of when it was done for iOS: #60109

[jmagman]

Some iOS work that would need to be done to work with macOS:

• create_macos_framework.py updated to create the xcframework Generate XCFramework in recipe package script engine#22664
• Add xcframework to ios out engine#22506
• Update archiving code
  https://github.com/flutter/engine/blob/a0906bdfc845ee4321e624d24e07a579a7b66432/ci/builders/mac_host_engine.json#L398-L400
  Ideally those artifacts would more closely match the structure of iOS since you're already touching this code, but that's a nice-to-have https://github.com/flutter/engine/blob/main/ci/builders/mac_ios_engine.json
• Add to downloaded Flutter SDK artifacts Add XCFramework artifacts #71113
• Use the xcframework in the tool Adopt Flutter.xcframework in tool #71495
  Fortunately you won't need logic like this because there will be only one "triple" in the FlutterMacOS.xcframework:
  

  flutter/packages/flutter_tools/bin/podhelper.rb

  Lines 80 to 86 in 2c56a25

  	next if xcframework_file.start_with?('.') # Hidden file, possibly on external disk.
  	if xcframework_file.end_with?('-simulator') # ios-arm64_x86_64-simulator
  	build_configuration.build_settings['FRAMEWORK_SEARCH_PATHS[sdk=iphonesimulator*]'] = "\"#{configuration_engine_dir}/#{xcframework_file}\" $(inherited)"
  	elsif xcframework_file.start_with?('ios-') # ios-arm64
  	build_configuration.build_settings['FRAMEWORK_SEARCH_PATHS[sdk=iphoneos*]'] = "\"#{configuration_engine_dir}/#{xcframework_file}\" $(inherited)"
  	# else Info.plist or another platform.
  	end

• Codesign the binaries on publication Add Flutter.xcframework binaries christopherfujino/codesign.py#1 https://github.com/christopherfujino/codesign.py/blob/4664bb0c85479cbc4516e9ed3c53f2be612b3a4b/codesign.py#L169C1-L170
• Stop building the xcframework on flutter build macos-framework and instead use the one in the artifact cache directly
  https://github.com/flutter/flutter/blob/2c56a25da3eeb031a580492fde3bd2ebcc33a111/packages/flutter_tools/lib/src/commands/build_macos_framework.dart#L244C37-L249

cc @christopherfujino

Related #70413

[stuartmorgan]

• create_macos_framework.py updated to create the xcframework

As long as we are reworking this script, changing artifacts, etc. it would be great if we could combine it with #70413, creating the structure described here

[jmagman]

Also before the old FlutterMacOS.framework can be removed, we'll need to let the Flutter release team know so they can update their roll scripts, and coordinate with the Fl@G team to make sure build rules are updated, if needed.