https://www.choge-blog.com/programming/flutter-xcodeのエラーを解決する方法/#toc2
sudo xcode-select --switch /Applications/Xcode.app/Contents/Developer
sudo xcodebuild -runFirstLaunch
flutter doctor」コマンドを実行すると、次のようなエラーが出ました。
[!] Xcode - develop for iOS and macOS
✗ Xcode installation is incomplete; a full installation is necessary for iOS
development.
Download at: https://developer.apple.com/xcode/download/
Or install Xcode via the App Store.
Once installed, run: