Add missing <string.h> include.

Change-Id: Iffdfed00ac49a7920844fa5f9e1a3ffc6a77e641
diff --git a/micro_bench/micro_bench.cpp b/micro_bench/micro_bench.cpp
index b4b3d42..fecd707 100644
--- a/micro_bench/micro_bench.cpp
+++ b/micro_bench/micro_bench.cpp
@@ -20,6 +20,7 @@
 
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
 #include <ctype.h>
 #include <math.h>
 #include <sched.h>