Fix gcc-6 build

- Include intrinsics polyfill in AVX512 vector binary micro-kernels

PiperOrigin-RevId: 285484657
diff --git a/src/f32-vbinary/gen/vmulc-avx512f-x16.c b/src/f32-vbinary/gen/vmulc-avx512f-x16.c
index 1a86801..7ff5e68 100644
--- a/src/f32-vbinary/gen/vmulc-avx512f-x16.c
+++ b/src/f32-vbinary/gen/vmulc-avx512f-x16.c
@@ -12,6 +12,7 @@
 #include <immintrin.h>
 
 #include <xnnpack/common.h>
+#include <xnnpack/intrinsics-polyfill.h>
 #include <xnnpack/vbinary.h>