Gradle build不会为Groovy源生成编译的二进制/类目录

Question

鉴于以下build.gradle：

apply plugin: 'groovy'
apply plugin: 'maven'

group = "myorg"

repositories {
    mavenCentral()
}

dependencies {
    compile 'org.codehaus.groovy:groovy-all:2.3.3'
    compile 'commons-io:commons-io:1.3.2'
    compile 'org.apache.httpcomponents:httpclient:4.3.5'
    compile 'org.slf4j:slf4j-api:1.7.5'

    testCompile 'junit:junit:4.11'
}

task sourcesJar(type: Jar, dependsOn: classes) {
    classifier = 'sources'
    from sourceSets.main.allSource
}

artifacts {
    archives sourcesJar
}

task wrapper(type: Wrapper) {
    gradleVersion = '1.11'
}

task dist(type: Zip, dependsOn: build) {
    classifier = 'buildreport'

    from('build/test-results') {
        include '*.xml'
        into 'tests'
    }

    from('build/reports/codenarc') {
        into 'reports'
    }

    from('build/docs') {
        into 'api'
    }

    from(sourcesJar) {
        into 'source'
    }

    from('build/libs') {
        exclude '*-sources.jar'
        into 'bin'
    }
}

task createPom << {

    pom {
        project {
            groupId "mygroup"
            artifactId "myservice-client"
            version version
        }
    }.writeTo("build/libs/pom.xml")
}

以下构建调用未创建build/classes/**/*目录：

gradle clean build sourcesJar createPom dist -Pversion=0.0.3

为什么吗