[clang] [Clang] Forward -rpath flag to the correct format in CPU offloading (PR #95763)

[Joseph Huber via cfe-commits]

jhuber6 wrote:

> > I thought that clang accepted `-rpath <path>`? I see that format when I try CPU offloading.
> 
> Yeah, but when running `--target=x86_64` and underlying gcc command is issued and complains about `-rpath <path>`

Oh, I see. When using `-fopenmp-targets=x86_64` it goes through the default GCC toolchain because you gave it no information. I'm wondering if we should bother supporting that since it's supposed to be `-fopenmp-targets=x86-64-unknown-linux-gnu` or similar. The GCC fallback isn't really guaranteed to work.

https://github.com/llvm/llvm-project/pull/95763