[Bug target/91472] gmp testsuite segfaults with gcc-8 and gcc-9, works fine with gcc-7

[matorola at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91472

--- Comment #1 from Anatoly Pugachev <matorola at gmail dot com> ---
compiling under gcc-8 but without "-O2" in CFLAGS makes it PASS instead of FAIL
(segfault).