test: Fix fence-image-self-test on Mac

On MacOS X, according to the manpage of mprotect(), "When a program
violates the protections of a page, it gets a SIGBUS or SIGSEGV
signal.", but fence-image-self-test was only accepting a SIGSEGV as
notification of invalid access.

Fixes fence-image-self-test

Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
2 files changed