title: Determine if a task is defined in an external build.gradle file
body: <p>I have a gradle task that is created at runtime to call another task ("myOtherTask") which is in a separate gradle file. The problem is if that other task doesn't exist an exception will be thrown. Is it possible to check that a task exists in an external gradle file before attempting to call it?</p>
  
  <p>Example:</p>
  
  <pre><code>  task mainTaskBlah(dependsOn: ':setupThings')
      task setupThings(){
      //...
      createMyOtherTask(/*...*/)
      //...
  }
  def createMyOtherTask(projName, appGradleDir) {
      def taskName = projName + 'blahTest'
      task "$taskName"(type: GradleBuild) {
          buildFile = appGradleDir + '/build.gradle'
          dir = appGradleDir
          tasks = ['myOtherTask']
      }
      mainTaskBlah.dependsOn "$taskName"
  }
  </code></pre>