[lld] [LLD][COFF] Detect weak reference cycles. (PR #104463)

[Martin Storsjö via llvm-commits]

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

The change looks good overall to me, so LGTM. But let's wait another day if there are further comments on the choice of container etc.

https://github.com/llvm/llvm-project/pull/104463