Building Grails 2.2.1 with Gradle, with Spock testing and Codenarc and some extra tasks to mimic Java/Groovy projects in Gradle

build.gradle

import org.grails.gradle.plugin.GrailsTask

apply plugin: 'grails'

grails {
    grailsVersion '2.2.1'
}

buildscript {
    repositories {
        mavenCentral()
        maven {
            name 'Grails Artifactory'
            url 'http://repo.grails.org/grails/repo'
        }
    }

    dependencies {
        classpath 'org.grails:grails-gradle-plugin:2.0.0-SNAPSHOT'
    }
}

repositories {
    mavenCentral()
    maven {
        name 'Grails Artifactory'
        url 'http://repo.grails.org/grails/repo'
    }
}

dependencies {
    bootstrap "org.grails.plugins:tomcat:${grails.grailsVersion}"

    compile 'org.grails.plugins:cache:1.0.1'
    compile 'org.grails.plugins:codenarc:0.9'
    
    runtime "org.grails.plugins:hibernate:${grails.grailsVersion}"
    runtime 'org.grails.plugins:resources:1.1.6'
    
    test "org.grails:grails-test:${grails.grailsVersion}"
    test('org.grails.plugins:spock:0.7') {
        exclude group: 'org.spockframework', module: 'spock-grails-support'
    }
    test 'org.spockframework:spock-grails-support:0.7-groovy-2.0'
}

task codenarcGrailsMain(type: GrailsTask) {
    command 'codenarc'
}

task codenarcMain(type: CodeNarc, dependsOn: codenarcGrailsMain) {
    codenarcGrailsMain.outputs.each {
        outputs.file it
    }
}

task codenarcGrailsTest(type: GrailsTask) << {}

task codenarcTest(type: CodeNarc, dependsOn: codenarcGrailsTest) {
    codenarcGrailsTest.outputs.each {
        outputs.file it
    }
}

task classes(type: GrailsTask) {
    command 'compile'
}

task build(dependsOn: [assemble, test]) << {}

test.dependsOn classes
assemble.dependsOn classes

This doesn't appear to work with gradle 2.8.
What version of gradle did you use?