Gradle: Define dependency in custom plugin

build.gradle

class Greeting implements Plugin<Project> {
    void apply(Project project) {
        project.task('first', type: FirstTask)
        project.task('second', type: SecondTask)
            .dependsOn('first')
    }
}

class FirstTask extends DefaultTask {
    @TaskAction
    def greet() {
        println 'first'
    }
}

class SecondTask extends DefaultTask {
    @TaskAction
    def greet() {
        println 'second'
    }
}

apply plugin: Greeting