[llvm] [ConstantMerge] Only merge constant w/unnamed_addr (PR #124050)

[via llvm-commits]

gulfemsavrun wrote:

I think the easier way to unblock this issue is to move `RelLookupTableConverterPass` after `ConstantMerge` in the LTO post-link pipeline as in https://github.com/llvm/llvm-project/pull/124053. Running this pass in LTO post-link step might also help this pass discover more opportunities.

https://github.com/llvm/llvm-project/pull/124050