gnat-6-sjlj-s390x-linux-gnu software package provides GNU Ada compiler (setjump/longjump runtime library), 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 gnat-6-sjlj-s390x-linux-gnu
gnat-6-sjlj-s390x-linux-gnu is installed in your system.
Make ensure the gnat-6-sjlj-s390x-linux-gnu package were installed using the commands given below,
$ sudo dpkg-query -l | grep gnat-6-sjlj-s390x-linux-gnu *
You will get with gnat-6-sjlj-s390x-linux-gnu package name, version, architecture and description in a table
| Distro | Debian 9 stretch |
| Section | Development |
| Package | gnat-6-sjlj-s390x-linux-gnu |
| Version | 6.1.1-9cross1 |
| Description | GNU Ada compiler (setjump/longjump runtime library) |
| Sub Section | devel |