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

[Joseph Huber via cfe-commits]

jhuber6 wrote:

> > Does Fedora only use default configurations when building its packages?
> 
> We try to stick to the defaults as much as possible. Having an implicit rpath by default causes issues when building other RPMs with clang, and typically, if we need to change something in order to build RPMS, we do it by adjusting the global C Flags used for building RPMS rather than patching the compiler.

We could make this logic more complicated by checking the system automatically `execute_command(lsb_release)` or something.

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