Error occurred trying to fall back to Cordova-lib execution

@cybernatic @a4anishm @syedtariq @larschla

I am pretty certain I've figured out the root cause to the issue. I ran cordova -v and saw this output -

Ross-MBP:test rossmartin$ cordova -v
/usr/local/lib/node_modules/cordova/node_modules/update-notifier/node_modules/configstore/index.js:53
				throw err;
				^

Error: EACCES: permission denied, open '/Users/rossmartin/.config/configstore/update-notifier-cordova.json'
You don't have access to this file.

I then ran

Ross-MBP:test rossmartin$ sudo chown -R rossmartin ~/.config
Ross-MBP:test rossmartin$ cordova -v
6.0.0

Now I see cordova reporting it is at 6.0.0 and can do ionic build/prepare again.

I think what happened is that the Ionic CLI did not think that the cordova CLI was installed as @a4anishm pointed out. Maybe it is possible that somewhere the Ionic CLI does a cordova -v and was getting hung up by the permission issue reading the ~/.config/configstore/update-notifier-cordova.json file.