[llvm] [AMDGPU][MC] Allow UC_VERSION_* constant reuse (PR #96461)

[Ivan Kosarev via llvm-commits]

https://github.com/kosarev approved this pull request.

LGTM, thanks! An error message or just removing the `assert(!Sym->isVariable() || ...` bit would be great.

> If we are not going to crash then, I believe we should give redefinition some defined/stable behaviour.

Yes, so just letting it use the new (possibly incorrect) value without crashing should be fine for now as we don't have any better options. But us not being able to prevent redefinition doesn't mean we want the user to believe that there is any particular asm/disasm behaviour to be expected if they try to.

> In which case this needs to use a different mechanism.

Yes. As soon as we have one.

https://github.com/llvm/llvm-project/pull/96461