strongswan: add missing dependency

Signed-off-by: Steven Barth <steven@midlink.org>

net/strongswan/Makefile

@@ -435,7 +435,7 @@ $(eval $(call BuildPlugin,aes,AES crypto,))
 $(eval $(call BuildPlugin,af-alg,AF_ALG crypto interface to Linux Crypto API,+kmod-crypto-user))
 $(eval $(call BuildPlugin,agent,SSH agent signing,))
 $(eval $(call BuildPlugin,attr,file based config,))
-$(eval $(call BuildPlugin,attr-sql,SQL based config,+strongswan-mod-sql))
+$(eval $(call BuildPlugin,attr-sql,SQL based config,+strongswan-mod-sql +strongswan-charon))
 $(eval $(call BuildPlugin,blowfish,Blowfish crypto,))
 $(eval $(call BuildPlugin,ccm,CCM AEAD wrapper crypto,))
 $(eval $(call BuildPlugin,cmac,CMAC crypto,))