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

[Sam Clegg via llvm-commits]

sbc100 wrote:

I think another approach would be to somehow run GlobalDCE (or something like that) after we generate all the `__cxa_atexit` calls.. I couldn't find a way to do that from `WebAssemblyPassConfig::addIRPasses` though, and this seems like a more direct appoach.

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