[llvm] [ValueTracking] Handle flipped strictness cases in `matchSelectPattern` (PR #121958)

[Nikita Popov via llvm-commits]

https://github.com/nikic commented:

Can you please land the move of getFlippedStrictnessPredicateAndConstant into ValueTracking separately from this change?

https://github.com/llvm/llvm-project/pull/121958