[llvm] [AMDGPU] Re-enable closed-world assumption as an opt-out feature (PR #115371)

[Shilei Tian via llvm-commits]

shiltian wrote:

I mean, whether they work or not doesn't really matter here. I'm not saying it doesn't work. They are just not officially supported. In all the cases we officially support, ABI linking will not be involved.

https://github.com/llvm/llvm-project/pull/115371