vppinfra: add COMPILE_TIME_CONST() macro

Type: improvement
Change-Id: I10d7489f57bc60eb92049962b4e6ea84974f17b8
Signed-off-by: Damjan Marion <damarion@cisco.com>
diff --git a/src/vppinfra/clib.h b/src/vppinfra/clib.h
index 05af8fe..4629a7d 100644
--- a/src/vppinfra/clib.h
+++ b/src/vppinfra/clib.h
@@ -120,6 +120,7 @@
 /* Hints to compiler about hot/cold code. */
 #define PREDICT_FALSE(x) __builtin_expect((x),0)
 #define PREDICT_TRUE(x) __builtin_expect((x),1)
+#define COMPILE_TIME_CONST(x) __builtin_constant_p (x)
 
 /*
  * Compiler barrier