Add missing includes.

Change-Id: Ibf549266a19a67eb9158d341a69dddfb654be669
diff --git a/linker/linker_environ.cpp b/linker/linker_environ.cpp
index daee56f..7272f4e 100644
--- a/linker/linker_environ.cpp
+++ b/linker/linker_environ.cpp
@@ -31,6 +31,7 @@
 #include <linux/auxvec.h>
 #include <stddef.h>
 #include <stdlib.h>
+#include <string.h>
 #include <unistd.h>
 
 #include "private/KernelArgumentBlock.h"