fixed the main 'die' proc to return error back to App (versus kill the whole app)

fixed the core 'die' function (executed whenever tcl encounters/throws a
fatal error), to return the 'error' back to the main app
(got rid of the 'exit -2', as this kills the tcl and the whole app!)...

instead the build terminates, throws the error, and leaves the app up in
the correct failed state...