spidermonkey: Disable tests on ARM

Some tests fail and cause kernel spam of this sort:

[ 6607.906159] Alignment trap: not handling instruction f4430a1f at [<0021e500>]
[ 6607.913308] Unhandled fault: alignment exception (0x811) at 0x003a15ec
[ 6607.919864] pgd = e8b88000
[ 6607.922601] [003a15ec] *pgd=fb185835