Generate HTML + Pdf with Asciidoctor Gradle plugin in the same build

build.gradle

buildscript {
    dependencies {
        classpath 'org.asciidoctor:asciidoctorj-pdf:1.5.0-alpha.11'
    }
}

plugins {
    id 'org.asciidoctor.convert' version '1.5.3'
}

apply plugin: 'java'
apply plugin: 'org.asciidoctor.convert'

version = '1.0.0-SNAPSHOT'

asciidoctorj {
    version = '1.5.4'
}

task buildHtml(type:org.asciidoctor.gradle.AsciidoctorTask){
    backends 'html5'
    attributes \
        'build-gradle': file('build.gradle'),
        'sourcedir': project.sourceSets.main.java.srcDirs[0],
        'endpoint-url': 'http://www.example.org',
        'source-highlighter': 'coderay',
        'imagesdir': './images',
        'toc': 'left',
        'icons': 'font',
        'setanchors': '',
        'idprefix': '',
        'idseparator': '-',
        'docinfo1': ''
    sources{
        include 'index.adoc'
    }
}

task buildPdf(type:org.asciidoctor.gradle.AsciidoctorTask, dependsOn:'buildHtml'){
    backends 'pdf'
    attributes \
        'build-gradle': file('pdf.gradle'),
            'sourcedir': project.sourceSets.main.java.srcDirs[0],
            'endpoint-url': 'http://www.example.org',
            'source-highlighter': 'coderay',
            'imagesdir': './images',
            'toc': 'left',
            'icons': 'font',
            'setanchors': '',
            'idprefix': '',
            'idseparator': '-',
            'docinfo1': '',
            'pdf-stylesdir': 'theme',
            'pdf-style': 'custom',
            'doctype': 'book'
    sources{
        include '**.adoc'
        exclude 'index.adoc'
    }
}

buildHtml.doLast {
    ant.move(file: 'build/asciidoc/html5', tofile: 'build/asciidoc/')
}

defaultTasks 'buildPdf'