As a side note (for the interested):
This question is interesting as it’s related to our latest build server update, where each docker image is now stored in the public registry, so that they can be used locally by our users.
Going forward, even though we’ll shut down old servers (6 months), we will still keep the images available for a lot longer (depending how many/large they are, it depends on cost).
Still, it allows for users to store them on their own, thus making their builds repeatable for as long as they wish.
However, there’s still the fact that you’ll then miss out on vital updates of platform sdk’s (e.g. iOS requirements to update for newer iOS versions etc, which isn’t uncommon)