[llvm] [Clang] Prevent `mlink-builtin-bitcode` from internalizing the RPC client (PR #118661)

[Shilei Tian via llvm-commits]

https://github.com/shiltian commented:

I think the change looks fine but I'm not an expert to judge if this is the best to way to do so.

@yxsamliu @Artem-B what do you folks think?

https://github.com/llvm/llvm-project/pull/118661