[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. 

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