Also multiple fixups:
- Fix structured attrs by removing it
- Switch to Flutter 3.16
- Add some comments on how to generate files
- Make patches apply more neatly
- Use proper cc
- Make output hash independant of metadata
- Softcode .so file ending
This is a second package to ensure people can still use the old one
which is built from a stable tag. The old 1.2.3 version uses a flutter
that is too old which is why it was dropped from nixpkgs.
