Integrate LLVM at llvm/llvm-project@18603319321a
Integrate LLVM at llvm/llvm-project@18603319321a

Updates LLVM usage to match
[18603319321a](https://github.com/llvm/llvm-project/commit/18603319321a)

PiperOrigin-RevId: 345513348

iree-org/iree,google/iree,iree-org/iree,iree-org/iree,iree-org/iree,google/iree,google/iree,google/iree,google/iree,iree-org/iree,google/iree,google/iree,iree-org/iree,iree-org/iree