This project intends to aggregate common or universal Xcode configuration settings, specifically for frameworks. Keeping them in hierarchical Xcode configuration files for easy modification and reuse. All build settings for platform-specific values are scoped by conditional variable assignments. This means you can have one framework target and select at build time, which platform it should be build against and the right default build settings are selected automatically.

Source: mrackwitz/xcconfigs: Universal Framework xcconfigs – build iOS, OS X, tvOS and watchOS frameworks on base of one target