[llvm] IR: Make llvm.fake.use a DefaultAttrsIntrinsic (PR #131743)

[Matt Arsenault via llvm-commits]

arsenm wrote:

> Besides the failing test (looks like it's just a matter of the fake.use attribute index shifting in `fake-use-determinism.c`), this LGTM. Just as a small check for posterity, is there a reason to use `IntrInaccessibleMemOnly` over `IntrNoMem` when we've also set `IntrHasSideEffects`?

I don't think so, I copied from something else. I'll fix it to IntrNoMem 

https://github.com/llvm/llvm-project/pull/131743