sna: Fix build on older GCC for cpuid()

We need to double check that the features we look for are supported by
the compiler before doing so.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

src/sna/sna_cpu.c

@@ -31,8 +31,14 @@
 
 #include "sna.h"
 
+#if defined(__GNUC__) && (__GNUC__ >= 4) /* 4.4 */
+
 #include <cpuid.h>
 
+#ifndef bit_AVX2
+#define bit_AVX2 (1<<5)
+#endif
+
 unsigned sna_cpu_detect(void)
 {
 	unsigned int eax, ebx, ecx, edx;
@@ -74,3 +80,12 @@ unsigned sna_cpu_detect(void)
 
 	return features;
 }
+
+#else
+
+unsigned sna_cpu_detect(void)
+{
+	return 0;
+}
+
+#endif