[lld] [ELF] Merge copyLocalSymbols and demoteLocalSymbolsInDiscardedSections (PR #69425)

[Paul Kirth via llvm-commits]

ilovepi wrote:

After bisecting it seems like bbf7b9d805f5773b4fe5bfb69081fe3691a90fb5 is when the issue crops up. 

Sorry for pinging the wrong PR. Our CI infra hasn't adapted to linkify github PR numbers yet, and I must have copied the wrong PR number. At least I pinged the right person, but still not great. I'll file a separate issue and CC you directly.

https://github.com/llvm/llvm-project/pull/69425