With minimal invasion I tried to get up and running with webapp-skel and found this problem:
The website generated for production tries to load ExtJS sources not from the static directory but from 3rdparty/ExtJS/src/app/Application.js (See the file ErrorinChromebrowser below).
The only thing I did was commenting in the app.js file (see index.diff) and adding a simple ExtJS to js/YourApp/app.js (see app.js).
If I add an Ext.require('Ext.Application') at the top of app.js I get this error during make production: