gnustep-back-common software package provides GNUstep GUI Backend - common files, you can install in your Debian 9 (Stretch) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install gnustep-back-common
gnustep-back-common is installed in your system.
Make ensure the gnustep-back-common package were installed using the commands given below,
$ sudo dpkg-query -l | grep gnustep-back-common *
You will get with gnustep-back-common package name, version, architecture and description in a table
| Distro | Debian 9 stretch |
| Section | GNUstep |
| Package | gnustep-back-common |
| Version | 0.25.0-2 |
| Description | GNUstep GUI Backend - common files |
| Sub Section | gnustep |