title: Cannot set the value of read-only property 'outputFile' for ApkVariantOutputImpl_Decorated with android studio 3.1.3
body: <blockquote>
    <p>Hello friends,
    <br/> I am facing one issue in app.gradle file when use proguard ruls with new android studio version is <code>3.1.3</code>. its working proper on old studio version <code>2.3.3</code>.<br/> My full error <code>Cannot set the value of read-only property 'outputFile' for ApkVariantOutputImpl_Decorated{apkData=Main{type=MAIN, fullName=debug, filters=[]}} of type com.android.build.gradle.internal.api.ApkVariantOutputImpl.</code></p>
  </blockquote>
  
  <p><strong>App.Gradle file:</strong><br/>
  <code>android {
   .....................
   buildTypes {
          release {
              minifyEnabled false
              proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
              applicationVariants.all { variant -&gt;
                  variant.outputs.each { output -&gt;
                      output.outputFile = new File(output.outputFile.parent, output.outputFile.name.replace(".apk", "-" + defaultConfig.versionName + ".apk"))
                  }
              }
          }
      }
  }</code></p>
  
  <p>Thnaks,</p>