[lld] [lld][ELF] Demote symbols in discarded sections to Undefined. (PR #68777)

[Peter Smith via llvm-commits]

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

Thanks very much for the updates. This looks good to me know. I think it is worth the maintainer @MaskRay taking a look first before merging.

https://github.com/llvm/llvm-project/pull/68777