Assets/Standard Assets/CrossPlatformInput/Scripts/MobileControlRig.cs(13,29): error CS0234: The type or namespace name IActiveBuildTargetChanged' does not exist in the namespace UnityEditor.Build’. Are you missing an assembly reference?
I had the same issue, but could resolve it by following this instruction (the answer provided by Jkfranzy1).
I didn’t delete the mentioned lines but commented.
BR,
Gregor