Not sure what's wrong, but those two build targets don't honestly do much. The web app build just gives you back your www folder in a ZIP file. The Chrome app gives you a basic chrome app with a starter manifest file. I recommend you do both by hand, those build targets aren't really doing much that's useful, developing Cordova and IoT apps are the most useful part of this tool.
The same overhere (again ;-) Can't build the WebApp anymore. Strange, it was working al the time...
I know it's just the www folder in ZIP format, but it was always a handy tool, just push the WebApp button and download the ZIP file for archiving the WebApp. Is there any change that this option will work again, or will it removed in the upcoming versions of XDK, like the many other build options (Amazon, etc)?
For now I can 'live' with Paul's solution, thanks for that!