[clang] [CMake] Link only the MLIR dialects ClangIR uses (PR #221616)

[Fangrui Song via cfe-commits]

MaskRay wrote:

> Thanks! I've been doing the same for Flang and was about to do this for CIR as well, your beat me to it :)

Haha! Thanks for the quick review!  In the near future I don't have any further CIR patches planned after this and #221797...

https://github.com/llvm/llvm-project/pull/221616