Note: we have an annoying situation currently where the docker containers are not hard-coded, so, if you build too long after others, you will get a different hash :-(

For example, the `v0.15.0.1` Docker ID needs to match what is listed here:
https://github.com/monero-project/gitian.sigs/pull/34

I should probably submit a PR to hardcode it and at least get the conversation started...