[llvm] Revert "[MC] Explicitly mark MCSymbol for MO_ExternalSymbol" (PR #133291)

[weiwei chen via llvm-commits]

weiweichen wrote:

> > Also, this is only a problem for X86, ARM64 backend is fine.
> 
> Because ARM64 marks the symbol external, or because of some inherent difference in asm between x86 and arm64, or because you have some other change that means you don't trip over it?
> 
> I still don't really understand why you think the right solution is to override the linkage of a symbol which already has a definition with an explicitly specified linkage.
> 
> > This change is needed for us to do so to make ORC JIT happy (just producing a *.o file for executable is also fine without this).
> 
> > here is more info on the error from ORC JIT
> 
> That sounds like a bug in ORC JIT: JIT linking should have the same semantics as regular linking, and an invalid input object file shouldn't cause an assertion failure.
> 
> I think we should just merge the straight revert for now. Then we explore the issues some more, and see if there's some better solution for whatever issue your "MCLinker" code is tripping over.

Ok, we will try to work on our side to find a different way to fix our issue. Though, this `MO_ExternalSymbol` is actually `internal` feels pretty weird. Shouldn't it be fixed somehow so that not more downstream projects have hacks on top this discrepancy?

https://github.com/llvm/llvm-project/pull/133291