title: Could not set unknown property 'mainClassName' for root project
body: <p>I am writing a spark application. With the following <code>build.gradle</code> file, I am getting an error as stated in the title when syncing gradle in Intellij Idea.</p>
  
  <pre><code>plugins {
    id 'java'
  }
  
  sourceCompatibility = 1.8
  
  mainClassName = 'HelloSpark'
  
  repositories {
    mavenCentral()
  }
  
  dependencies {
  ....
  }
  </code></pre>