Buildbot delay in flathub.json

I created a Github workflow that updates the generated-sources.json file of the packaged Rust application in every PR by flathubbot. This workflow takes a short time to finish, but the buildbot starts immediately after the PR gets created (and will fail, since it uses the not yet updated generated-sources.json).

Is there an option in flathub.json to delay the build for a few minutes, or even better to wait for another action to finish first?

Best regards