Short answer:
Alt/Option + Product menu> Clear (it will become "Clear build folder")
Trying to apply this answer , I previously installed the “Defines the module” in the “Packaging” section to “Yes” for my Build Settings application in Xcode 6.4. Then, trying to apply this answer , I re-opened my project in beta version of Xcode 7.0. That's when I got the error.
@stephencelis Alt/Option "" "", . " " . , , , .