ci: Use lld or gold instead of ld.bfd
We should be able to reduce our CI build times by using the lld or gold linkers. I haven't timed a full build like CI does, but un-ccached "touch a file and time rebuild with ccache disabled" on debugoptimized locally was:
- nir_lower_io.c: -52.5338% +/- 2.28666% (n=5)
- fd6_gmem.c: -49.8033% +/- 4.86371% (n=5)