The path to the BB10 SDK has got nothing to do with application-descriptor.xml
file so I don't quite understand why would it complain about it there.
Here is a question with this same error; The problem in this case was about using an incorrect SDK version: IBM Worklight 6.0 - "WebWorks SDK source file was not found" error
- For BlackBerry 6 and 7, use: https://developer.blackberry.com/bbos/html5/downloads/?os=mac#smartphones
- For BlackBerry 10, use: https://developer.blackberry.com/html5/downloads/?os=mac#blackberry10
Also note that Worklight does not officially support BB10 WebWorks SDK 2.0 beta.
So make sure to use the previous version (1.0.4.11 - direct download link), perhaps it will help in solving this.
I would also make sure that your WEBWORKS_HOME environment variable indeed points to the correct location; In my - working - setup it points to: C:\Program Files\Research In Motion\BlackBerry 10 WebWorks SDK 1.0.4.11