Add missing <string.h> include.

Change-Id: I79a9a58904b2992c306d8de0c7b3a4aacd4b67e0
diff --git a/verifier_test.cpp b/verifier_test.cpp
index e2f3d10..93a071e 100644
--- a/verifier_test.cpp
+++ b/verifier_test.cpp
@@ -19,6 +19,7 @@
 #include <stdarg.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
 #include <sys/types.h>
 #include <sys/stat.h>