title: error MSB1001: Unknown switch - Visual Studio 2017 RC
body: <p>When compiling my solution in Visual Studio 2017 RC I get </p>
  
  <pre><code>C:\Code\src\MSBUILD : error MSB1001: Unknown switch.
    Switch: -
  
    For switch syntax, type "MSBuild /help"
  </code></pre>
  
  <p>On every project.</p>
  
  <p>I can compile the solution using Visual Studio 2015. I have changed the build output to 'Diagnostic' and this is still all that I see.</p>