[lld] [lld] Merge equivalent symbols found during ICF (PR #134342)

[Nico Weber via llvm-commits]

nico wrote:

@pranavk If you could reply to https://issues.chromium.org/issues/415810137#comment44 that'd be cool :)

(We've now seen a problem from this on android too.)

https://github.com/llvm/llvm-project/pull/134342