LibraryPlugin.groovy

// jar the classes.
            Jar jar = project.tasks.create("package${buildType.name.capitalize()}Jar", Jar);
            jar.dependsOn variantData.javaCompileTask, variantData.processJavaResourcesTask
            jar.from(variantData.javaCompileTask.outputs);
            jar.from(variantData.processJavaResourcesTask.destinationDir)

            jar.destinationDir = project.file(
                    "$project.buildDir/$DIR_BUNDLES/${variantData.variantConfiguration.dirName}")
            jar.archiveName = "classes.jar"