Log Message:
Fix unprivileged builds.

When USE_BSD_MAKEFILE is set, pkgsrc will automatically pass all *OWN
and *GRP vars to the underlying make.  In unprivileged.mk one will find
that pkgsrc sets, for example, BINOWN to UNPRIVILEGED_USER, i.e. the
current (unprivileged) user if nothing else was specified.

Thanks to gdt, joerg and asau!