Make the option structures const.

Signed-off-by: Jan Engelhardt <jengelh@gmx.de>
diff --git a/extensions/libip6t_rt.c b/extensions/libip6t_rt.c
index a36c65a..3c3911e 100644
--- a/extensions/libip6t_rt.c
+++ b/extensions/libip6t_rt.c
@@ -29,7 +29,7 @@
 IPTABLES_VERSION, IP6T_RT_HOPS);
 }
 
-static struct option opts[] = {
+static const struct option opts[] = {
 	{ "rt-type", 1, 0, '1' },
 	{ "rt-segsleft", 1, 0, '2' },
 	{ "rt-len", 1, 0, '3' },