[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:

> At the least, can you add a comment about the intended use and the risk of using this improperly? Is it possible to guard by the target triple or something indicating that it is compiling for AMDGPU?

Will do a follow-up PR for this.

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