title: Artifact is not published using gradle and artifactory plugin
body: <p>I'm trying to upload a simple zip to artifactory using gradle. This is my script:</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-html lang-html prettyprint-override"><code>buildscript {
    repositories {
      jcenter()
    }
    dependencies {
      classpath "org.jfrog.buildinfo:build-info-extractor-gradle:latest.release"
    }
  }
  apply plugin: 'com.jfrog.artifactory'
  apply plugin: 'maven-publish'
  
  def user = "$System.env.ARTIFACTORY_USER"
  def pass = "$System.env.ARTIFACTORY_PASSWORD"
  
  task createArchive(type: Zip){
   baseName 'myzip'
   destinationDir(new File('target'))
   from '.'
   exclude 'target'
   exclude '.gradle'
   exclude 'build.gradle'
   exclude 'README.md'
   doFirst{
    new File('target').mkdirs()
   }
  }
  
  task clean(type: Delete){
   delete 'target'
  }
  
  publishing {
      publications {
          customArtifact(MavenPublication) {
              artifact createArchive
          }
      }
  }
  
  artifactory {
      publish {
          contextUrl = 'http://myrepo/artifactory'
          repository {
              repoKey = "myrepo-tools"
              username = user
              password = pass
          }
          publications ('customArtifact')
      }
  }</code></pre>
  </div>
  </div>
  </p>
  
  <p>The code seems to work fine but actually only the build info are published. The zip is not:</p>
  
  <pre><code>Deploying build descriptor to: http://myrepo/artifactory/api/build
  Build successfully deployed. Browse it in Artifactory under http://myrepo/artifactory/webapp/builds/myproject/1503338121156
  </code></pre>
  
  <p>My code does not seem different from the one published here: <a href="https://stackoverflow.com/questions/25258174/how-to-build-groovy-jar-w-gradle-and-publish-it-to-in-house-repo/25260461#25260461">How to build Groovy JAR w/ Gradle and publish it to in-house repo</a> (which was pointed as reference in question <a href="https://stackoverflow.com/questions/25279001/nothing-published-to-artifactory-using-gradle-artifactory-plugin">nothing published to artifactory using gradle artifactory plugin</a>) but I'm not sure that is still valid since is quite old.</p>
  
  <p>The main difference is that almost all the examples are using java plugin so they have the <code>from components.java</code> line in the publications. In my case I cannot use it as I have a custom zip.. but I can't find what else can be changed.</p>
  
  <p>Thanks,
  Michele.</p>