[clang] [clang][Driver][OpenMP] Add -f[no-]openmp-implicit-rpath flag (PR #215532)

[Joseph Huber via cfe-commits]

https://github.com/jhuber6 requested changes to this pull request.

We already have `-rtlib-add-rpath` for this, which adds this for the per-target runtime dir. We should fix this in two ways. 1. AMD starts using `LLVM_ENABLE_PER_TARGET_RUNTIME_DIR` and the build of `libomiptarget` itslef needs to add a proper rpath to the installed library directory.

https://github.com/llvm/llvm-project/pull/215532