[lld] [WIP][lld] Add lld warning for checking discarded sections via COMDAT (PR #74151)

[Roland McGrath via llvm-commits]

frobtech wrote:

I concur with Peter's assessment. This is far more strict than the actual requirement, and I'm skeptical it's useful even as an opt-in check because it's so strict.  Something like verifying that all alternate groups define all the same non-local symbols is I think the strongest check that can be enforced in the general case.

https://github.com/llvm/llvm-project/pull/74151