Integrate build into upstream repos, as much as possible

[danngreen]

These projects currently use a CMake script to build the project as a MetaModule plugin.
Sometimes a fork of the original VCV Rack source is used, and sometimes the unmodified original is used.

Ideally the build script could live in source repo, with a new build target for MM plugin. The build script would need to be provided a path to the MM SDK (similar to how you have to specify the Rack SDK path to build a Rack plugin).