[clang] [Clang][OpenMP] Fix multi arch compilation for -march option (PR #92290)

[Joseph Huber via cfe-commits]

jhuber6 wrote:

> > > If `-march` is the wrong option then let's start deprecating it and remove it altogether in the next llvm release. But, as long as it is here, it should be equivalent to `--offload-arch`.
> > 
> > 
> > Honestly not a bad idea. I could make a patch warning users to use `--offload-arch` instead for now.
> 
> Sure, let's do that. But, let this land as long as this option is supported.

That doesn't track, LLVM has never supported `-march` to support multiple options and there's no reason to add it now when we're talking about deprecating it.

https://github.com/llvm/llvm-project/pull/92290