title: Integrating FxCop Gives an error : FAKE F#MAKE
body: <p>I am using FxCop in FAKE but it is giving an error 
  i.e. </p>
  
  <p><code>Analysis was not performed; at least one valid rules assembly and one valid target file must be specified.
  * 1 total analysis engine exceptions.</code></p>
  
  <p>While all targets are successfully build.</p>
  
  <p>here is my code :</p>
  
  <pre><code>    Target "FxCop" (fun _ -&gt;
      !! (buildDir + "/**/*.dll")
          ++ (buildDir + "/**/*.exe")
          |&gt; FxCop (fun p -&gt;
              {p with
                  //Override default parameters
                  ReportFileName = testDir + "FXCopResults.xml";
  
                  ToolPath = "D:/Fake/FAKE-Calculator/tools/FxCop/FxCopCmd.exe"})
  )
  </code></pre>
  
  <p>It also shows : <strong>Project error</strong> : No targets were selected .</p>