Docker and singularity containers

[Pjotr Prins]

I know this is not a priority right now for maintainers, but I think
it would be really useful if we provide ready-made containers for
certain packages. This will allow people who have the infrastructure
to run containers to start using reproducible Guix builds. With that,
I think there will be an increased interest in our technology.

Maybe it is something to discuss at FOSDEM, but I wonder what it would
take to have the build farm automatically provide Docker containers
for marked packages and offer them through the web interface.

Unlike substitutes we only need to hold the last version. People can
provide their own infrastructure to retain/share them.

Pj.