Salsa CI: Add extra test to validate that 'adduser' can be used
My intent was to introduce a generalized test to detect issues such as in https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1098508 but it does not seem to trigger the right condition.. This provably works now, and can be merged and used to vet next uploads.
Edited by Otto Kekäläinen