[lld] [LLD] [COFF] Fix crashes for cfguard with undefined weak symbols (PR #79063)

[via llvm-commits]

alvinhochun wrote:

Do you have an example stack trace of the codepath that triggers the error? I wonder if `maybeAddAddressTakenFunction` is supposed to prevent this from happening in the first place. If the problematic codepath bypasses this function and calls `addSymbolToRVASet` directly, then maybe it shouldn't...

https://github.com/llvm/llvm-project/pull/79063