iwmmxt: Don't define dummy _mm_empty for >=gcc-4.8
Definition was not present in <4.8.
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=55451
diff --git a/pixman/pixman-mmx.c b/pixman/pixman-mmx.c
index febf95a..e678ce5 100644
--- a/pixman/pixman-mmx.c
+++ b/pixman/pixman-mmx.c
@@ -51,7 +51,7 @@
#define CHECKPOINT()
#endif
-#ifdef USE_ARM_IWMMXT
+#if defined USE_ARM_IWMMXT && __GNUC__ == 4 && __GNUC_MINOR__ < 8
/* Empty the multimedia state. For some reason, ARM's mmintrin.h doesn't provide this. */
extern __inline void __attribute__((__gnu_inline__, __always_inline__, __artificial__))
_mm_empty (void)
