[clang] [Clang] Add 'CLANG_ALLOW_IMPLICIT_RPATH' to enable toolchain use of -rpath (PR #82004)

[Joseph Huber via cfe-commits]

jhuber6 wrote:

> I don't think a CMake option is the right way to go here. For example, I doubt we would actually use this CMake option in Fedora if this patch is committed.

Does Fedora only use default configurations when building its packages?

> Does gcc use rpath for libgomp?

That's irrelevant to the needs of projects like `libomptarget` or other HIP libraries. We do not have these problems with `libomp` because it is a mostly stable ABI, so if users pick up the wrong one (Which happens all the time) no one notices and we don't get bug reports.

https://github.com/llvm/llvm-project/pull/82004