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

[Michał Górny via llvm-commits]

mgorny wrote:

> Uhh, do those go through the runtime build?

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 `libc_path` ends up being:

```
/usr/lib/llvm/21/lib64/cmake/llvm/../../../libc
```

> If you copy it back does it work?

I can only test it partially right now — after restoring the file from the preceding commit, it fails due to missing files from `libc/src` instead, since we're doing a sparse checkout. To extend the checkout, I'd have to stop the container and it has some more jobs going on right now. That said, it feels a bit contrary to its purpose for files from "shared" to include files from "non-shared" part of libc.

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.

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