[clang] [clang][CodeGen] Skip deleted globals in emitUsed (PR #210959)

[Aaron Ballman via cfe-commits]

AaronBallman wrote:

> > @vgvassilev @efriedma-quic this is approved and CI is green is there anything else we need on this one before it can land? Thanks!
> 
> Aaron added @asl afterwards and I wanted to give him a chance to look. Let's wait for another week and we can land it...

I added Anton in case Eli was busy, but Eli approved as a codegen code owner, so I think it's fine to land on that LG if you're comfortable.

https://github.com/llvm/llvm-project/pull/210959