cups: fix to support duplex printing on PS printers
Due to a missing build dependency duplex printing
on Postscript printers was broken.
This update fixes this issue.
- Submitted by Stefan Brüns (StefanBruens)
Fixed bugs
bnc#776080
poppler > 0.18.0 regression: no longer duplex printing on PostScript printers (works with poppler 0.18.0)