Xcode Build Settings has a Build Active Architecture Only for every project/target. It’s useful when getting a performance gain while debugging.
NO – If set to no, then it will build on all the architectures.
If there’s no problem, setting to YES will make building faster. During debug mode this is perfectly fine. In release mode not so much. Unless you know the kind of devices that will be used to run your app then I don’t think it is wise to ever set this to YES for release mode. For an example, I built a project with Build Active Architecture Only set to YES for release mode. I ended up with an error while trying to install my app on an iPhone 5C which has a different architecture than an iPhone 6S. Yikes! Don’t have one of those it works on my machine moments. Avoid it and be careful!