[libc] [llvm] [libc] Make RPC server handling header only (PR #131205)

[Joseph Huber via llvm-commits]

jhuber6 wrote:

> If I understand the question correctly, then no — we build straight from `offload` directory.
> 
> > I think that might be a side-effect of me moving where the FindLLVMLibcCommonUtils.cmake file lived. It used to be in runtimes/ but I put it in llvm.
> 
> Ah, yes, that explains it. Since the file is part of installed LLVM, `CMAKE_CURRENT_LIST_DIR` is not the source path and

All that file does is point to the `libc/` directory and set `-DLIBC_NAMEPACE=something`. That shouldn't be too difficult to make work, because that standalone build should still have an LLVM tree as far as I'm aware. Worst case scenario we detect if we're doing this standalone build and just mask it out.

> Also, if you wanted to move it out of `runtimes`, then perhaps the shared top-level `cmake` directory would work better. `llvm/cmake` is really only for stuff that ought to be installed.

Good point.

https://github.com/llvm/llvm-project/pull/131205