[lld] [LowerGlobalDtors] Skip __cxa_atexit call completely when arg0 is unused (PR #68758)

[Dan Gohman via llvm-commits]

sunfishcode wrote:

The change here looks good to me. I like how it does automatic detection so it avoids needing a flag.

https://github.com/llvm/llvm-project/pull/68758