package missing include for string.h

package.c gets string.h inherited from
private/android_filesystem_config.h it should
not rely on this in the future. The intent is
to move fs_config function into libcutils and
thus deprecate any need for string.h in this
include file.

Bug: 19908228
Change-Id: I5db6d0a88c5b1eb9f582284e9bdd220c096ea69a
diff --git a/run-as/package.c b/run-as/package.c
index 4f8f3a7..9e1f5bb 100644
--- a/run-as/package.c
+++ b/run-as/package.c
@@ -16,9 +16,11 @@
 */
 #include <errno.h>
 #include <fcntl.h>
-#include <unistd.h>
-#include <sys/stat.h>
+#include <string.h>
 #include <sys/mman.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
 #include <private/android_filesystem_config.h>
 #include "package.h"