As of today, print/cups-pstoraster do not support staging despite mandatory usage required before end of june 2014.
Fix: Here's a patch that add staging and fix a few things based on portlint suggestion.
How-To-Repeat: make -C /usr/ports/print/cups-pstoraster stage
Over to maintainer (via the GNATS Auto Assign Tool)
Committed with some changes. Thanks!