Currently, you need the cfx tool to build add-ons if you want to use the Addon SDK. The build process includes mapping dependencies, adding in the bootstrap.js
file for restartless addons, and a few files to make it loadable via Firefox. Just zipping it and calling it a xpi won't do the trick.
The Addon-SDK team is looking at options to make the same directory structure that you use for development able to be loaded directly into Firefox, removing the build step: Proposal
I worked on a JS-only builder addon during the SDK work week a few weeks ago that involves an addon essentially building and installing another addon. You can probably pull out components of that and node-ify them if you can run node on your build server. What -is- available on that other machine? What are you trying to accomplish that this set up is necessary, with a machine that doesn't even have python installed?