My Xcode project is setup in a way that has multiple configurations, allowing me to use the same code base for different variations of my app, but have unique elements in ea
This is what you can do to make this work:
EXCLUDED_SOURCE_FILE_NAMES
User-Defined setting.By doing this, Xcode will only compile the appropriate asset catalogs, and ignore the others. I've tested this on one of our projects, and it works as intended.
Good luck!
REMARK: If you are using CocoaPods, you might run into troubles because CocoaPods adds a build step of its own to compile your assets, and those of your dependencies into on .car file. See https://github.com/CocoaPods/CocoaPods/issues/1546 for the discussion on this issue. TL;DR: make sure this step doesn't execute in your build phase, or edit the CocoaPods script they execute to not do the asset building.
UPDATE 1/19/2019: With the latest stable Xcode (10.1) and Cocoapods (v1.5.3) they work out of the box with the solution above. No need to alter the Cocoapods scripts or build steps, just set EXCLUDED_SOURCE_FILE_NAMES
as described.