Explicitly enable altivec if it's supported. vect_int tests for
powerpc_altivec_ok, but without the explicit option, if altivec is not
enabled by default, we end up expecting vectorization that doesn't
occur.
for gcc/testsuite/ChangeLog
* gcc.dg/signbit-2.c: Add -maltivec if supported.
/* This test does not work when the truth type does not match vector type. */
/* { dg-additional-options "-mno-avx512f" { target { i?86-*-* x86_64-*-* } } } */
/* { dg-additional-options "-march=armv8-a" { target aarch64_sve } } */
+/* { dg-additional-options "-maltivec" { target powerpc_altivec_ok } } */
/* { dg-skip-if "no fallback for MVE" { arm_mve } } */
#include <stdint.h>