Improve --auto_diff mode for when GMA is the only changed SDK. #10944

Job	Run time
check_and_prepare	14s
build-ios-macos-13	1h 43m 6s
build-tvos-macos-13	1h 22m 38s
build-android-ubuntu-20.04	56m 55s
build-desktop-ubuntu-20.04-x64-openssl	35m 34s
build-android-macos-13	1h 9m 10s
build-desktop-macos-13-x64-openssl	1h 16m 44s
build-android-windows-latest	1h 17m 15s
build-desktop-windows-latest-x64-openssl	1h 26m 14s
test-android-ubuntu-20.04-android_target-gameloop	25m 12s
test-android-ubuntu-20.04-emulator_ftl_target-gameloop	10m 38s
test-android-macos-13-android_target-gameloop	34m 26s
test-android-macos-13-emulator_ftl_target-gameloop	8m 37s
test-android-windows-latest-android_target-gameloop	28m 10s
test-android-windows-latest-emulator_ftl_target-gameloop	10m 51s
test-tvos-macos-13-tvos_simulator	15m 53s
test-desktop-ubuntu-20.04-x64-openssl	3m 30s
test-desktop-${{ matrix.os }}-${{ matrix.arch }}-${{ matrix.ssl_variant }}-custom-runner	0s
test-desktop-macos-13-x64-openssl	4m 57s
test-desktop-windows-latest-x64-openssl	14m 12s
test-ios-macos-13-ios_target-gameloop	15m 0s
test-ios-macos-13-simulator_target-gameloop	32m 25s
summarize-results	10s
attempt-retry	0s
	13h 11m 51s

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