CI: add multi-distro build (using docker)

[fermino]

This PR adds a github-actions job that builds rmlint on several distros, mostly to check compatibility against toolchain and libraries (and avoid stalling issues like #605).

If there is any other distro that could be added please let me know.

[vassilit]

This is not a distro, but FreeBSD would be great.

[fermino]

This is not a distro, but FreeBSD would be great.

I looked into it but right now it's a bit convoluted, there's this which could work though: https://github.com/marketplace/actions/freebsd-vm

[vassilit]

Cirrus-CI has a good FreeBSD support that is free AFAIK for open-source projects

[RayOei]

I don't know how complete (@fermino) you want these builds to be?
I noticed that

• most distros (except debian & ubuntu) don't build the manpage because of Unable to find sphinx binary in PATH
• some warnings for scons (except Debian & Ubuntu):
  scons: Reading SConscript files ... /build/SConstruct:831: SyntaxWarning: invalid escape sequence '\.' 'sed -i "s/2\.0\.0/{v}/g" po/rmlint.pot', /build/SConstruct:832: SyntaxWarning: invalid escape sequence '\(' 'sed -i "s/^Version:\(\s*\)2\.0\.0/Version:\\1{v}/g" pkg/fedora/rmlint.spec'
• Use apt-get instead of apt in the Debian section - this will not trigger the apt warning in the build
• Some complain about: '/bin/sh: line 1: git: command not found
  Checking for git revision... Unable to find git revision.`

And, obviously, these warning/errors are not picked up as such.

[fermino]

@RayOei I mostly wanted to make sure that things are building properly as some things have been breaking in arch and gentoo (and IIRC there is some soon to be packaging issues in debian).

Thanks for looking into those messages, I will fix what I can and get back with whatever's left :)

[vassilit]

Something useful would be to build on macOS (intel, arm) and also on 32bit architectures.