Regenerate linux/netfilter_ipv6/ip6_tables.h.

Add ip6t_get_target() to kernel_known_generic_statics in
libc/kernel/tools/defaults.py to be able to build ip6tables.

Change-Id: Iadb885db3faa85b2d0070dc2e0ac493af6e62bb6
diff --git a/libc/kernel/tools/defaults.py b/libc/kernel/tools/defaults.py
index 4227de7..b35f72b 100644
--- a/libc/kernel/tools/defaults.py
+++ b/libc/kernel/tools/defaults.py
@@ -71,6 +71,7 @@
           "__cmsg_nxthdr",                    # linux/socket.h
           "cmsg_nxthdr",                      # linux/socket.h
           "ipt_get_target",
+          "ip6t_get_target",
         ]
     )