Integrate LLVM at llvm/llvm-project@def99ad68bce
Integrate LLVM at llvm/llvm-project@def99ad68bce

Updates LLVM usage to match
[def99ad68bce](https://github.com/llvm/llvm-project/commit/def99ad68bce)

PiperOrigin-RevId: 353222879

google-research/structured-additive-IR,google-research/structured-additive-IR