Adds flags for testability, only to build active architecture, and bakes the app package name into the project file. All this to fix the warnings generated by XCode.
This also drops the flags for architecture completely as there is only one valid variation for tvOS and not setting it gives the default.
I had some issues getting it to be set at all. Plus, considering that apps compiled without it will not even run on the devices I can't see any reason for keeping it around.
