CI: sign artifacts only on branches of this repository #9
Description
The GitHub workflow for this project will attempt to sign the generated artifacts. That will fail if the workflow runs on a branch that does not belong to this repository (but a fork instead, which is typically where PRs originate).
The signing fails, because those repositories do not have the secret values needed to perform the signage.
When running in different repositories, the workflow shouldn't attempt to sign the artifacts.