[clang] [Clang] Make `-Xarch_` handling generic for all toolchains (PR #125421)

[Artem Belevich via cfe-commits]

Artem-B wrote:

> --offload-arch= isn't an accepted -cc1 argument so it won't be forwarded at all.

Silently? That would be wrong, imo. It should be diagnosed somewhere.

https://github.com/llvm/llvm-project/pull/125421