I'm still of the idea that these should be moved to the XCScheme class. This class is oriented to edit xcodeprojs.

>  I imagined create a method inside of AbstractTarget because if you try create a new scheme by Xcode you must select which target is the build target for this new scheme. 

Notice that in Xcode you don't configure the schemes in the same view that you use to configure the build settings and the build phases of a target. This has nothing to with the target other than taking it as a parameter. Xcode uses a dedicated UI for the schemes where you select the target. So in my opinion the above code should be moved to helper methods of `XCScheme` which take the targets as arguments.