I created a build tool for similar reasons, difference being that it's aimed at Cakefile users. It's goal is to be as simples as possible, support common tasks out of the box (minifying, compiling LESS/coffee/etc) and should work on Windows too:
I could see shelljs as a stand-alone executable using JSDB (http://jsdb.org) too, should be an easy port, cross-platform, much smaller and dependency-free.
http://github.com/ricardobeat/cake-flour
I could see shelljs as a stand-alone executable using JSDB (http://jsdb.org) too, should be an easy port, cross-platform, much smaller and dependency-free.