Integrate LLVM at llvm/llvm-project@b999400a4fb6
Integrate LLVM at llvm/llvm-project@b999400a4fb6

Updates LLVM usage to match
[b999400a4fb6](https://github.com/llvm/llvm-project/commit/b999400a4fb6)

PiperOrigin-RevId: 328096769

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