[ffigen] Failure on weekly arm64 bot

[liamappelbe]

https://github.com/dart-lang/native/actions/runs/11087954105/job/30807210350

[dcharkes]

❌ /Users/runner/work/native/native/pkgs/ffigen/test/native_objc_test/isolate_test.dart: isolate Manual release across isolates (failed)
❌ /Users/runner/work/native/native/pkgs/ffigen/test/native_objc_test/isolate_test.dart: isolate Use after release and double release (failed)
❌ /Users/runner/work/native/native/pkgs/ffigen/test/large_integration_tests/large_objc_test.dart: Large ObjC integration test (failed)

Looks like the failures are related specifically to objc.

[liamappelbe]

There are fixes in #1616 and #1618 that should fix this. Not sure how to rerun the bot at head. Maybe we'll just wait until it reruns itself.