Integrate LLVM at llvm/llvm-project@2668714747c5
Integrate LLVM at llvm/llvm-project@2668714747c5

Updates LLVM usage to match
[2668714747c5](https://github.com/llvm/llvm-project/commit/2668714747c5)

PiperOrigin-RevId: 355292910

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