strongswan: fix forecast plugin dependency

The forecast plugin does not require the iptables binary, it uses
libiptc instead.

Signed-off-by: Stijn Tintel <stijn@linux-ipv6.be>
(cherry picked from commit 6e132e74fd)

net/strongswan/Makefile

@@ -687,7 +687,7 @@ $(eval $(call BuildPlugin,eap-radius,EAP RADIUS auth,))
 $(eval $(call BuildPlugin,eap-tls,EAP TLS auth,+strongswan-libtls))
 $(eval $(call BuildPlugin,farp,fake arp respsonses,))
 $(eval $(call BuildPlugin,fips-prf,FIPS PRF crypto,+strongswan-mod-sha1))
-$(eval $(call BuildPlugin,forecast,forward multi/broadcast traffic,+iptables-legacy +kmod-ipt-conntrack-extra))
+$(eval $(call BuildPlugin,forecast,forward multi/broadcast traffic,+libip4tc +kmod-ipt-conntrack-extra))
 $(eval $(call BuildPlugin,gcm,GCM AEAD wrapper crypto,))
 $(eval $(call BuildPlugin,gcrypt,libgcrypt,+PACKAGE_strongswan-mod-gcrypt:libgcrypt))
 $(eval $(call BuildPlugin,gmp,libgmp,+PACKAGE_strongswan-mod-gmp:libgmp))