[llvm] [LV] Fix for miscompile with disjoint or (PR #81922)

[via llvm-commits]

https://github.com/annamthomas commented:

Landing the updated test case separately and closing this MR in favour of the linked one (changes disjoint or to add in poisonDroppingFlags API).

https://github.com/llvm/llvm-project/pull/81922