Script build flow

[zultron]

Right now, when starting from a Docker image, it takes a number of steps to get to the final Apt repo with binary packages for all arches: build chroot, build source package, build amd64 package, build i386 package, build armhf package, update Apt repo.

This single-package sequence should be scripted.

It would also be nice to have a sequence to build a string of packages and their deps, and be smart about pkgs not applicable to some distros or arches. (E.g. RTAI applicable to x86 but not ARM; Cython applicable to Wheezy but not Jessie.)

[zultron]

Fixed with #21