This plugin is no longer actively maintained. J2ObjC Gradle Plugin: enables Java source to be part of an iOS application's build so you can write an app's non-UI code (such as application logic and data models) in Java, which is then shared by Android apps (natively Java) and iOS apps (using J2ObjC), all as part of your usual Android Gradle build.
Until #568 is fixed, the plugin should warn explaining the reason for the failure.