[llvm] [CodeGen] Get stack alignment from TargetFrameLowering (NFCI) (PR #105477)

[Nikita Popov via llvm-commits]

nikic wrote:

This looks reasonable to me. If we're in the backend, we should query backend data structures.

Note that we also have things like the `override-stack-alignment` module flag, which TFL takes into account, while DL can't.

https://github.com/llvm/llvm-project/pull/105477