[llvm] [InstCombine] Drop poison-generating flags in `threadBinOpOverSelect` (PR #87230)

[Yingwei Zheng via llvm-commits]

dtcxzyw wrote:

Compile time impact: http://llvm-compile-time-tracker.com/compare.php?from=d76a1233f7d7923d056a53cfa6f89735e9cda86e&to=900106267f135c4e3c5a6f744096e61dd94f3e44&stat=instructions%3Au

https://github.com/llvm/llvm-project/pull/87230