[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.

This hangs with this patch:
```clang -target x86_64-unknown-linux-gnu -O1 -g -c hang.c```
[hang.c.gz](https://github.com/user-attachments/files/26673873/hang.c.gz)


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