The officially sanctioned way to get memcpy() is to #include <string.h>.

Change-Id: Ie157d9305df5f9b86a09ea2224666fd2c054cda4
diff --git a/libcore/luni/src/main/native/org_apache_harmony_luni_platform_OSNetworkSystem.cpp b/libcore/luni/src/main/native/org_apache_harmony_luni_platform_OSNetworkSystem.cpp
index 904b935..3390880 100644
--- a/libcore/luni/src/main/native/org_apache_harmony_luni_platform_OSNetworkSystem.cpp
+++ b/libcore/luni/src/main/native/org_apache_harmony_luni_platform_OSNetworkSystem.cpp
@@ -35,6 +35,7 @@
 #include <netinet/tcp.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
 #include <sys/ioctl.h>
 #include <sys/socket.h>
 #include <sys/time.h>