[clang] Revert "[CIR] Add math and builtin intrinsics support (#175233)" (PR #180916)

[Andrzej Warzyński via cfe-commits]

banach-space wrote:

I suspect that it will be a very easy fix, but I'm out of cycles today to take a further look myself, hence proposing to revert.

https://github.com/llvm/llvm-project/pull/180916