[llvm] [ValueTracking] Handle not cond to assume. (PR #127140)

[Andreas Jonson via llvm-commits]

andjo403 wrote:

But my proposal to use findValuesAffectedByCondition also is no good as it removes the assume in https://github.com/llvm/llvm-project/blob/538b8f8008b95782ea1967284e22500c72aec67d/llvm/test/Transforms/GVN/assume.ll#L48-L61 as the `%icmp` is not ephemeral as there is a user that is not ephemeral

https://github.com/llvm/llvm-project/pull/127140