[lld] [LLD][ELF] Fix SHF_MERGE misalignment when spilled (PR #119289)

[Peter Smith via llvm-commits]

https://github.com/smithp35 approved this pull request.

LGTM too.

One thing that made me think is the update to the OutputSection addralign. I initially thought that we'd be at risk of increasing OutputSection alignment for the PotentialSections that aren't used, however on reflection I think we have to do that to make sure we converge.

https://github.com/llvm/llvm-project/pull/119289