[llvm] [InstCombine] Fold `select Cond, not X, X` into `Cond ^ X` (PR #90089)

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AtariDreams wrote:

This food gives me a few more ideas. Particularly it takes me back to that rejected PR. Perhaps I could use this property somehow to fold expressions regarding bitwise nots of each other...

https://github.com/llvm/llvm-project/pull/90089