[llvm] [clang] [CMake] Move check for dlfcn.h and dladdr to clang (PR #76163)

[Abhina Sree via cfe-commits]

abhina-sree wrote:

> Can you say what motivated this? Change looks fine, but it looks like it fixes a problem someone reported somewhere but this doesn't say what the problem is.

Yes, there was a concern about exposing prefix-less macros in the llvm-config.h here https://github.com/llvm/llvm-project/pull/75928#issuecomment-1865290992

https://github.com/llvm/llvm-project/pull/76163