test:semmc-ppc-tests performance regression with recent z3s

[RyanGlScott]

If I run test:semmc-ppc-tests with z3-4.8.8, then it completes in about one minute or so. With z3-4.8.9, however, it runs significantly slower—I ran it for about five minutes before ultimately giving up. (If I had waited long enough, it would have likely finished after a while, but it is still dog slow.) I've observed this phenomenon with z3 versions 4.8.9, 4.8.10, and 4.8.14.