title: sbt 0.13.16 - How do I println(systemProperty) in build.sbt file?
body: <p>I am migrating a Build.scala file to a build.sbt file.</p>
  
  <p>In the Build.scala file, there are print statements that print out vals (of type String) defined in the body of the Build.scala file. </p>
  
  <p>project/Build.scala:</p>
  
  <pre><code>import sbt._
  import Keys._
  
  object HelloBuild extends Build {
      val foo = System.getProperty("foo")
      println(foo)
  }
  </code></pre>
  
  <p>How do I migrate these print statements to the build.sbt file?</p>