If you're going to use memset...

...you'd better #include <string.h>.

Change-Id: I83e0877f4151fc764588e2d876e66d7712d41f61
diff --git a/libc/bionic/pthread_exit.cpp b/libc/bionic/pthread_exit.cpp
index afda089..3401ed7 100644
--- a/libc/bionic/pthread_exit.cpp
+++ b/libc/bionic/pthread_exit.cpp
@@ -30,6 +30,7 @@
 
 #include <signal.h>
 #include <stdlib.h>
+#include <string.h>
 #include <sys/mman.h>
 
 #include "pthread_internal.h"