We currently don't have a nice open source API for building node apps, but would welcome PRs that get us in this direction!

There are two ways to build a node app using the XAR builder tools. 1. Use the `make_xar` tool which will create a XAR from a directory and takes an optional script to run on execution. 2. Use the XAR builder library to make a XAR builder that is specialized for building node apps.