I always suspected the overflow conversions were UB, but with gcc doing
different things on arm, I thought it was about time to abandon those
particular tests. What I was not expecting was for the return value of
strcmp to be "UB" (in that there's no guarantee of the exact value, just
< = > 0). Fortunately, nothing actually relies on the value of the op
other than the tests, so modify the test to make the behavior well
defined.