In mail/postfix, there are options sasl and dovecot-sasl.  Enabling just
dovecot-sasl results in a broken build because the smtpd.conf config
file is needed but not created.  I cannot figure out easily which of
this is generic to all sasl and which to dovecot vs cyrus.

I don't know why this just failed; I would think I've been rebuilding
postfix fairly often.

ob-tech-pkg: is there some way to indicated that option foo requires
option bar, other than forcing an error if foo and not bar?