snapd is not tested against Arch Linux

[Zygmunt Krynicki]

Spread supports Arch Linux but our test suite is not actively exercised against it. A quick rough look at this suggests that the following steps must be taken:

 [ ] Define an Arch (x86_64) system in linode in spread.yaml
 [ ] Add Arch-specific prepare code for packaging, etc
 [ ] Put distribution specific commands in conditional sections with their Arch equivalents
 [ ] Blacklist tests that rely on confinement
 [ ] Blacklist tests that rely on Ubuntu-specific features (if any)

Ideally it would be good to add an Arch image to https://github.com/zyga/spread-qemu-images so that development can be done against locally-running qemu target.

This bug is a clone of the following github issue: https://github.com/snapcore/snapd/issues/2552

[Maciej Borzecki (maciek-borzecki)]

Some initial work in this PR: https://github.com/snapcore/snapd/pull/4285 and a relevant forum topic: https://forum.snapcraft.io/t/integrate-arch-linux-into-ci-pipeline/2904

[Maciej Borzecki (maciek-borzecki)]

We're pretty close this time: https://github.com/snapcore/snapd/pull/4989