title: Android Gradle 3.0.0-alpha2 plugin, Cannot set the value of read-only property 'outputFile'
body: <p>i was using  this code<br></p>
  
  <pre><code>applicationVariants.all { variant -&gt; 
      variant.outputs.each { output -&gt;
          def SEP = "_"
          def flavor = variant.productFlavors[0].name
          def buildType = 
          variant.variantData.variantConfiguration.buildType.name
          def version = variant.versionName
          def date = new Date()
          def formattedDate = date.format('ddMMyy_HHmm')
          def newApkName = PROJECT_NAME + SEP + flavor + SEP + buildType + SEP + version + SEP + formattedDate + ".apk"
          def file = new File(newApkName)
          output.outputFile = file
      }
  }
  </code></pre>
  
  <p><br> to change the name of apk file when i build new apk, but since i use the <strong>Android Studio 3.0 Canary 2</strong> this error appear:<br>
  <strong>Cannot set the value of read-only property 'outputFile'....</strong></p>