Align amd64 subarches with psABI / glibc 2.33

[Artoria2e5]

The glibc people have fixed the "cripple amd" haswell issue by introducing some platform-neutral ABI generations to amd64. See https://sourceware.org/bugzilla/show_bug.cgi?id=23249.

We should probably align our arch defs to the new values, although it might be easier to do after the changes go into gcc and clang. I don't think we need alternative lib installations yet, so overlays are fine to me for now.