compatible: feat: expose ubuntu-version in build_charms_with_cache.yaml

[DnPlas]

Expose ubuntu-version as an input for running the workflow on a specific ubuntu version. This parameter is used in the runs-on field, and can be configured by other workflows.

[carlcsaposs-canonical]

Out of curiosity, can I ask what situation you're encountering where you'd like to change the runs-on version? (i.e. needing ubuntu-20.04, for self-hosted runners, etc.)

FYI the build job does not use charmcraft destructive mode, so it should be able to build on multiple Ubuntu versions

[DnPlas]

Out of curiosity, can I ask what situation you're encountering where you'd like to change the runs-on version? (i.e. needing ubuntu-20.04, for self-hosted runners, etc.)

FYI the build job does not use charmcraft destructive mode, so it should be able to build on multiple Ubuntu versions

Yes, our charms (charmed-kubeflow) for instance have base 20.04, and we needed to pin those versions in our ci. If no destructive mode is used, maybe we can avoid this parameter as the build should be agnostic to the Ubuntu version, as you say. Feel free to close this PR if the contribution doesn't make sense.

[carlcsaposs-canonical]

The workflow should be able to build 20.04 charms while running on ubuntu-latest. We'll likely re-open this when we need to add support for self-hosted runners

Please re-open if you have any issues building 20.04 charms!