Main entry point for the builder application.
If you wish to run Cityscape Builder interactively, try the following:

(interactive-builder-init)

The either: (interactive-builder-main) ; for a context + main loop

Or: (opengl-context-start) ; for a context
and: (builder-main-loop) ; for a main loop

Then there is a (leave-builder-main-loop) function, to leave it when running in it, as well as:
(opengl-context-stop/start/restart)
to cleanly stop/start the OpenGL context.