[lld] [ELF] Suppress --no-allow-shlib-undefined diagnostic when a SharedSymbol is overridden by a hidden visibility Defined which is later discarded (PR #70130)

[Peter Smith via llvm-commits]

smithp35 wrote:

> See also the Discourse post [Relocatable file definitions shared with DSO](https://discourse.llvm.org/t/relocatable-file-definitions-shared-with-dso/74391)

Not had a chance to look at the code yet. I've replied on the Discourse post, hopefully I understood it correctly.

https://github.com/llvm/llvm-project/pull/70130