class ClasspathPlugin implements Plugin<Project> {
    void apply(Project project) {
        project.task('printClasspath') {
            doLast {
                project
                    .rootProject
                    .allprojects
                    .configurations
                    .flatten()
                    .findAll { it.name.endsWith('Classpath') }
                    .collect { it.resolve() }
                    .flatten()
                    .unique()
                    .findAll { it.exists() }
                    .each { println it }
            }
        }
    }
}

rootProject {
    apply plugin: ClasspathPlugin
}