[llvm] [PowerPC] Do not merge TLS constants within PPCMergeStringPool.cpp (PR #94059)

[Nikita Popov via llvm-commits]

nikic wrote:

Why does PPC need a custom pass for this instead of using the general GlobalMerge pass? It seems like all the requirements already present in GlobalMerge get rediscovered here step by step.

Note that the sanitizer-ppc64be-linux buildbot has regular crashes in this pass, but not on every build, so I don't think this is the last issue affecting this pass.

https://github.com/llvm/llvm-project/pull/94059