[clang] [llvm] [SystemZ, Clang] Enable verification of int args extensions by default. (PR #223755)

[Ulrich Weigand via cfe-commits]

https://github.com/uweigand approved this pull request.

This now LGTM in general, thanks.   There's a few cosmetic things in the error output that would be good to fix, see inline.

https://github.com/llvm/llvm-project/pull/223755