build script: initial crude attempt at incremental testing
build script: initial crude attempt at incremental testing

Doing this right requires a lot more work, starting with plugins to
dynamically discover the list of fubsy/* packages and loop over them.
This is a useful first attempt, though, and it's good enough for a
small project with a fast compiler and fast tests.

sbinet/fubsy,sbinet/fubsy,sbinet/fubsy,sbinet/fubsy,sbinet/fubsy