Add missing includes.

Change-Id: Ibf549266a19a67eb9158d341a69dddfb654be669
diff --git a/libc/bionic/bionic_systrace.cpp b/libc/bionic/bionic_systrace.cpp
index c74a52c..10521cf 100644
--- a/libc/bionic/bionic_systrace.cpp
+++ b/libc/bionic/bionic_systrace.cpp
@@ -19,6 +19,7 @@
 #include <fcntl.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
 
 #include "private/bionic_systrace.h"
 #include "private/libc_logging.h"