The Port pulls in libssh as a depedency regradless of options. I could build successful the port with all options except RPKI on a clean system without libssh.
Created attachment 199175 [details] proposed patch
A commit references this bug: Author: olivier Date: Mon Nov 12 22:30:20 UTC 2018 New revision: 484845 URL: https://svnweb.freebsd.org/changeset/ports/484845 Log: libssh is a dependency of RPKI option PR: 233170 Submitted by: dinoex Changes: head/net/bird2/Makefile
Thanks!