Fix for https://bugs.llvm.org/show_bug.cgi?id=31181. When LFTR moves a condition prior to increment to a condition after increment, it may depend on a value that is now poison due to nowrap flags. We need to make sure to drop the nowrap flags on the add in such a situation. I'm doing this by copying the nowrap flags that SCEV computed.
Once this issue is fixed, we can reenable computation of nowrap flags in CVP.