title: Display exact scala command issued from SBT build
body: <p>When I build my (relatively complex) SBT project against a local version of Scala, I am getting the following error:</p>
  
  <pre><code>scalac error: bad option: '-Ydelambdafy:method'
  </code></pre>
  
  <p>This is potentially a bug in <code>scalac</code> or our buildfile. However, I am unable to reproduce this error while invoking <code>scalac</code> directly:</p>
  
  <pre><code>$ scalac -Ydelambdafy:method test.scala
  </code></pre>
  
  <p>This runs as expected. Is there a way I can make SBT display the exact <code>scalac</code> command it issues? (Note that passing the exact flags from <code>scalacOptions</code> to <code>scalac</code> also does not result in the error).</p>
  
  <p><code>scalacOptions</code> is:</p>
  
  <pre><code>List(
    -deprecation,
    -unchecked,
    -feature,
    -encoding, utf8,
    -Ydelambdafy:method,
    -Xplugin:&lt;...&gt;/scala-js-test/compiler/target/scala-2.11.0-RC1/scalajs-compiler_2.11.0-RC1-0.4.1-SNAPSHOT.jar)`
  )
  </code></pre>
  
  <p>The repository in question is the <code>scalajs-library</code> subproject of the <a href="https://github.com/scala-js/scala-js" rel="nofollow">Scala.js master</a> with a build of the current <a href="https://github.com/scala/scala" rel="nofollow">Scala master</a> as <code>scalaHome</code>.</p>
  
  <p>To configure the project for this build, issue:</p>
  
  <pre><code>set every List(scalaHome := Some(file("&lt;scalaHome&gt;")), scalaVersion := "2.11.0-RC1")
  </code></pre>
  
  <p>in the root project.</p>