[llvm] [MC,CodeGen] Update .prefalign for symbol-based preferred alignment (PR #184032)

[Mikael Holmen via llvm-commits]

mikaelholmen wrote:

Hi @MaskRay 

Heads-up that I've bisected a case where the compiler hangs with this patch. I'll try to extract a reproducer.

https://github.com/llvm/llvm-project/pull/184032