This makes it possible to build on any platform that supports Linux
containers. The container image used for building is created once, or on
updating the `scripts/Dockerfile.build` and is cached afterwards.
To build the executable in a container, use `make containerized-build`
and everything will be done automatically. The executable will also be
available on the usual location.
Signed-off-by: Niels de Vos <ndevos@redhat.com>
