Github workflow: upload snapcraft logs if build step fails

[pieqq]

Description

When the GIthub actions in charge of building a snap (checkbox runtime, checkbox) fail, no logs are uploaded because the upload-artifact action is not run if the previous step fails. Using a condition in the upload-artifact job to fix this:

https://github.com/actions/upload-artifact#conditional-artifact-upload

Including /home/runner/.local/state/snapcraft/log/ dir as well since this seems to be what snapcraft is doing now:
https://github.com/canonical/checkbox/actions/runs/5329296264/jobs/9654916215#step:6:144

Starting Snapcraft 7.4.3
Logging execution to '/home/runner/.local/state/snapcraft/log/snapcraft-20230621-022645.823345.log'
Snap file not available for arch 'arm64'.
Build log available at 'checkbox18_arm64.txt'
Build failed for arch 'arm64'.
(...)

Resolved issues

Documentation

Tests

[Hook25]

+1