Fixed compilation with LibreSSL

[abakay]

Hi @jbeverly,

Recently I had problem with security/pam_ssh_agent_auth port on FreeBSD 12.1 with LibreSSL 3.1.4. The port itself compiled fine, but during runtime it gave the following error:

sudo: in try_dlopen(): /usr/local/lib/pam_ssh_agent_auth.so: (null): Undefined symbol "RSA_get0_e"

This is due LibreSSL doesn't have 'RSA_get0_*’ function(s). So, I did little correction, compile it on FreeBSD 12.1-RELEASE-p8 as port and it is working with LibreSSL 3.1.4.

Could you please review my changes below and let me know could it be merged?

Originally posted by @abakay in #27

Thanks,
Andriy