We install the rust toolchain, but then we have to manually
source it in CI since the headless containers skip over
the shell profiles that rustup typically uses.
Ideally we'd set these as variables in the main image, but
we don't have access to the buildah instance used in
ci-templates/cbuild.
However adding them to the toolbox image is good enough to
have the toolbox setup work ootb even if it doesn't call the
ci/scripts/source_image_env.sh script like the gitlab-ci jobs
will do.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/7816>
Previously the script will give you a command like:
```
toolbox create gst-toolbox ..
```
Which is a bit redundant since we are already creating
toolbox, we don't need to label it as such.
Now instead use gst-$GST_UPSTREAM_BRANCH for the name,
so we will suggest gst-main and gst-1.24 instead
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/7816>
This is mostly done to remove the hardcoded HOME
env var that ci-templates appends to the image. See [1]
[1] https://gitlab.freedesktop.org/gstreamer/gstreamer/-/issues/2433#note_2243222
But it also allows us to add extra things useful for local
development to it, as long they don't interfere with the
build enviornment.
This also means we can switch the build image to be based
on top of the normal fedora one rather than toolbox,
so it will no longer advertise the toolbox compatible labels
since it was buggy anyway.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/7455>
