Making a port: doesn't know "make depends"?

[Scott I. Remick]

So I was dabbling with a program not in the ports tree. Actually pulling
off a successful port myself is probably outside of my abilities, however
I figured I'd explore the steps to create a pkg-list so that I could know
what files it put on my system so I could back it out if need be.

I was looking at the instructions here:
http://www.freebsd.org/doc/en_US.ISO8859-1/books/porters-handbook/porting-autoplist.html

But hit a snag:

su-2.05b# make depends PREFIX=/var/tmp/gift-ares
make: don't know how to make depends. Stop

I did some searching and couldn't find an answer, so I ask here... what to
do when a port doesn't know how to "make depends"?