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

[Joseph Huber via cfe-commits]

jhuber6 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.

It's already an error if you pass it directly via -`Xclang` because it's not an accepted `-cc1` argument. A lot of driver arguments are both driver and `cc1` arguments so those get marshalled or forwarded.

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