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

[Jon Chesterfield via cfe-commits]

JonChesterfield wrote:

Enable by default without cmake and fedora run their own patch is my preferred solution.

The Siemens dev working on gcc amdgpu offloading told me they set rpath on the executable at a conference but I haven't checked their implementation. His attitude was that programs should be able to run without setting environment variables.

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