The fwbuilder makefile specifies devel/rcs as a run dependency for
FreeBSD 10 and later, but the specification is ignored on a stock
FreeBSD 10.3 installed from an ISO. At some point rcs was removed
before FreeBSD-10 release, but it seems to have been put back and
controlled with a build knob, so it may or may not be present on
FreeBSD 10 or later.
Change the test from checking OSVERSION to checking for the existence
of /usr/bin/rcs. It's a better chek and it fixes a potential dependency
mismatch issue between the port and the built package.
While here, change RUN_DEPENDS= to RUN_DEPENDS+= to avoid a potential
overwrite of existing values.
Approved by: infrastructure blanket (redundant deps work)
044e3a6784