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

[Artem Belevich via cfe-commits]

Artem-B wrote:

> I don't think there's any use of --offload-arch outside of the driver. 

I agree. Yet we do need to deal with such nonsensical input in a consistent manner. We do not control what the users give us, but we control how we respond.

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