[clang] RFC: [cmake] Export CLANG_RESOURCE_DIR in ClangConfig (PR #97197)

[Kim Gräsman via cfe-commits]

kimgr wrote:

@tstellar 
> I think that the GetResourcesPath function is incorrect. There's no reason it should return a wrong value, since the CLANG_RESOURCE_DIR value is always known at compile time.

Please see https://github.com/llvm/llvm-project/pull/103388 for an attempt to make this internally consistent.

https://github.com/llvm/llvm-project/pull/97197