[llvm] Add CMake configure preset building blocks (PR #170019)

[Aaron Ballman via llvm-commits]

AaronBallman wrote:

I've added a few CMake maintainers as reviewers; I don't know enough about CMake to feel comfortable saying yes or no to this, but the changes *looked* reasonable to me FWIW.

https://github.com/llvm/llvm-project/pull/170019