[llvm] CodeGen: Respect function align attribute if less than preferred alignment. (PR #149444)

[Hans Wennborg via llvm-commits]

zmodem wrote:

> If asan requires higher alignment for some reason, we should model that in the compiler somewhere (maybe in the asan lowering pass).

In our bug, it's actually not the asan-instrumented code that required 16-byte alignment, but the asan runtime itself. So regardless of this change, we should probably pass -falign-functions` to request that explicitly: https://github.com/llvm/llvm-project/pull/154694

https://github.com/llvm/llvm-project/pull/149444