[clang] [SystemZ][z/OS] Implement z/OS XPLINK ABI (PR #91384)

[Ulrich Weigand via cfe-commits]

https://github.com/uweigand commented:

This version LGTM now, I think once the transparent-union thing is resolved, this should be ready to commit.  Thanks!

https://github.com/llvm/llvm-project/pull/91384