Debian packages based on Bullseye

[lmoureaux]

Is your feature request related to a problem? Please describe. We document support for Debian Bullseye, but the packages we build are based on Ubuntu 22.04 and depend on libraries newer than what can be found on Bullseye even with backports enabled (esp. libc6 and libstdc++). This causes some trouble with systems stuck on older versions, e.g. ChromeOS (#1973)

Describe the solution you'd like and Describe alternatives you've considered We could provide CI builds based on Bullseye, but this would quickly add up. Maybe I should resurrect the effort with the Open Build Service.

[lmoureaux]

I investigated again using the OpenSUSE's Open Build Service (OBS). I created Debian, Ubuntu, and OpenSUSE packages for 3.0.2: https://build.opensuse.org/repositories/home:louis94_m:freeciv21/freeciv21 I haven't tested them yet.

About the setup:

• OBS needs a few configuration files in order to operate. They're stored and versioned at OBS, but we can't use git. I think a parallel repo for the files would be needed.
• When doing a release we'd update versions in the "OBS config" repo and that would basically be it.
• It's possible to trigger OBS builds from Github webhooks so we could create "nightly" (or more realistically "weekly") repositories
• Supported distros are Debian, OpenSUSE, SUSE Entreprise, Scientific Linux, RHEL, Fedora, CentOS, Mageia, AppImage, Univention (?), IBM, Ubuntu, openEuler, Raspian, Arch