[llvm] [ElimAvailExtern] Add an option to allow to convert global variables in a specified address space to local (PR #144287)

[Shilei Tian via llvm-commits]

shiltian wrote:

> also note the github-actions warning about undef / poison.

Yeah, but I think we'd want to keep that `undef` since it is the initializer for the global variable.

https://github.com/llvm/llvm-project/pull/144287