Update to kernel headers v4.12.3.

Test: Built angler.
Change-Id: Icbcf4fac2334de8409b049ed7a3b4c24b4e98ce9
diff --git a/libc/kernel/uapi/linux/ipv6_route.h b/libc/kernel/uapi/linux/ipv6_route.h
index 56bc659..b7271a7 100644
--- a/libc/kernel/uapi/linux/ipv6_route.h
+++ b/libc/kernel/uapi/linux/ipv6_route.h
@@ -19,6 +19,7 @@
 #ifndef _UAPI_LINUX_IPV6_ROUTE_H
 #define _UAPI_LINUX_IPV6_ROUTE_H
 #include <linux/types.h>
+#include <linux/in6.h>
 #define RTF_DEFAULT 0x00010000
 #define RTF_ALLONLINK 0x00020000
 #define RTF_ADDRCONF 0x00040000