Now we will pick up the right gstreamer branch + namespace when
building an image, and also the right (matching, if any) cerbero
branch + namespace.
This solves the bootstrapping issue when doing an image update that
requires coordination between gstreamer and cerbero.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/5043>
Main differences with previous setup are:
- No manifest creation
- gst-indent is executed only when the bot is assigned (instead of the manifest task)
- Cerbero jobs are triggered in the cerbero repo
- Remove cerbero and android related files as they now are in cerbero
itself.
- Update `container.ps1` to the new file layout
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/891>
