GitHub actions improved: releases works as a repo

[tqre]

I worked some on our CI/CD pipeline:

• The VM image is now an artifact that can be downloaded for inspection
• Tests are now a separated job, and the resulting VM is a qcow2 based on the first image - only changes are recorded
• The releases page works now as a pacman repository, instructions under 'Binary repository' on main README file
• Some naming changes and clarifications on descriptions

Here is a resulting releases page from my fork, the pacman database files are new: https://github.com/tqre/selinux/releases/tag/ArchLinux-SELinux

And here is a link to artifacts (need to be signed in to GitHub to view): https://github.com/tqre/selinux/actions/runs/507124264

I tested to bootstrap a fresh Arch with SELinux support straight from above page, and it works like a charm.

Some todos as a reminder for the future:

• sign the repo
• things still to work on from PR #67: .BUILDINFO packager and test commands/script

[tqre]

Seems like this is a commonly occurring bug - Uploading artifacts fail. Reported this here: https://github.com/actions/upload-artifact/issues/154

On my branch everything worked out as it was supposed to...

[fishilico]

This looks great! And the repository works very nicely!

Two small comments when reading the changes:

• The image used to test some commands is named archselinux.qcow2. This name is not very clear and could be confusing (the "Arch Linux VM with SELinux support" is archlinux.qcow2). Could you please change the name of this file, for example to test_arch_selinux_cmd.qcow2?
• prepare_release could be run everytime, in order to ensure that creating the pacman repository still works, in Pull Requests and in forked repositories. If you agree, could you please remove if: github.ref == 'refs/heads/master' from prepare_release (while keeping it in release).

Otherwise, this is really a great work, which is easy to understand and easy to use (thanks for the documentation in the README about the generated Arch Linux repository!)

[tqre]

Thanks for comments. I did the modifications you suggested:

Rename the VM files: archselinux.qcow2 is the base image which has SELinux support bootstrapped in. archselinux_test.qcow2 is the filename that has the test phase induced modifications recorded relative to the base image.

Removed the if clause from the prepare_release -step.

[fishilico]

Thanks! I rebased your commits on top of master and pushed them on https://github.com/archlinuxhardened/selinux/commits/315e0d4c4f5ba194540658c95fbca57ecc206686