title: Change outputfile using new 'outputs' property in 0.13.0
body: <p>Just updated my android project to latest android gradle plugin and changed the script since there are some deprecated methods. However, I got <code>argument type mismatch</code> error when I tried to build the project. I found that something was wrong when I tried to change the <code>outputfile</code> name, the following is part of script in 'build.gradle':</p>
  
  <pre><code>android.applicationVariants.all { variant -&gt;
  
     def apkName = target;
     if (variant.buildType.name == "release") {
        apkName += "-RELEASE.apk";
     } else {
        apkName += "-DEBUG.apk"
     }
  
     // this is the line caused type mismatch error
     variant.outputs.outputFile = file("$project.buildDir/outputs/apk/" + apkName)
  }
  </code></pre>
  
  <p>I tried to changed to 
       <code>variant.outputs.outputFile = "$project.buildDir/outputs/apk/" + apkName</code>
  but it's not working.  </p>
  
  <p>How to fix it?</p>