Add missing includes.

Change-Id: I06ea08400efa511e627be37a4fd70fbdfadea2e6
diff --git a/updater/updater.c b/updater/updater.c
index 465e123..661f695 100644
--- a/updater/updater.c
+++ b/updater/updater.c
@@ -17,6 +17,7 @@
 #include <stdio.h>
 #include <unistd.h>
 #include <stdlib.h>
+#include <string.h>
 
 #include "edify/expr.h"
 #include "updater.h"