Base: FreeBSD 12.0-RELEASE-p6 GENERIC amd64
The port stops building with:
makeinfo: unrecognized option `--css-ref=/share/site.css'
Try `makeinfo --help' for more information.
gmake: *** [Makefile:586: gnupg.info] Error 1
gmake: *** Waiting for unfinished jobs....
I can't replicate it, so I'll need more information than those four lines. A good start would be the full build log, the list of ports you have installed, information about how you're building (i.e. what program you're using to build it), and the contents of your /etc/make.conf.