Xcode 8 and Preprocessor Macros
Try "Clean build" first... if that doesn't work then try
In the Preprocessor Macros Not Used in Precompiled Headers there are two subheadings
Preprocessor Macros Not Used in Precompiled Headers
debug +
release +
With a plus appearing beside when you hover over them. Press the plus on both of these and you should get:
Preprocessor Macros Not Used in Precompiled Headers
debug +
Any Architecture | Any SDK
release +
Any Architecture | Any SDK
You don't need to enter anything here after you have pressed +. Once you have added these two extra entries, try another clean build.
It was an actual bug in XCode 8. With XCode 9 (as of today, Sep 2017 beta 6), it is finally resolved.