Mechanism for build() in mybinder?

I have a package of tutorials. I can use the package locally by

using Pkg; Pkg.activate("."); Pkg.instantiate()

This builds the tutorial notebooks.

How do I get these notebooks built on mybinder?

I got it to work with postBuild (, but I’m not sure if that’s the right solution. So far so good, so perhaps it will be useful to someone else as well.