ati-drivers: Restore opengl & direct rendering

- Removed a collision in the nix store
- Removed dependency on qt
- Fixed opengl and direct rendering by correcting some link paths
- Some code refactored in builder.sh
- Comments added/modified

This pull request fixes #11740 and I recommend that it be considered
as a hotfix for the stable channel due to the fact that opengl
and direct rendering are broken there too.