We are aware of this issue and are providing a fix for it with the next release of the AppBuilder extension for Visual Studio
which is due in the next couple of weeks.
As a workaround till then I'd suggest that you:
1.) Install the AppBuilder CLI
on your OS X host
2.) Make your project accessible from your OS X host
3.) Manually build and deploy it to the iOS emulator following the steps here
Let me know if this helps and do not hesitate to contact us if you have further questions.