[llvm] [IR] Don't create ptrtoint expression to determine alignment (NFCI) (PR #161364)

[Alexander Richardson via llvm-commits]

https://github.com/arichardson approved this pull request.

I think this should be disabled for unstable pointers since the value could in theory be changed by the GC between intoptr and use but that can wait. Change LGTM

https://github.com/llvm/llvm-project/pull/161364