The man page of bsd.port.mk, particular PORTS_PRIVSEP provides this suggestion
'permit nopass setenv {....} user cmd pkg_add' I don't know much about what pkg_add can do, but when building packages with many dependencies, password prompt greets for every dependency, persist option doesn't work across the dependencies for the above command, so it becomes a pain in the ass. I think persist doesn't work because of the setenv part, since it is different for every package/sub-package What do you suggest?