Define NDEBUG before including any headers.

bench/bench-klib.c

@@ -1,3 +1,5 @@
+#define NDEBUG
+
 #include <stdlib.h>
 #include <stdio.h>
 #include <stdbool.h>
@@ -5,8 +7,6 @@
 #include <sys/resource.h>
 #include <sys/time.h>
 
-#define NDEBUG
-
 #include "kvec.h"
 #include "klist.h"
 #include "kbtree.h"