title: Reference a heat generated wxs file from a merge module
body: <p>I want to create a trivial merge module that contains all the files of a directory called "build" and installs them to the program files folder. I will use heat to generate a wxs file with all these files, and I want this to be separated from the wxs file I edit manually for the merge module. How do I reference the heat generated file from my other merge module wxs file?</p>
  
  <p>I generate my heat wxs file like this:</p>
  
  <pre><code>heat dir build -cg heatComponent -gg -var var.buildFolder -dr ProgramFilesFolder -srd -out heatComponent.wxs
  </code></pre>
  
  <p>I know how to create an msi file of this:</p>
  
  <pre><code>&lt;Wix xmlns="http://schemas.microsoft.com/wix/2006/wi"&gt;
      &lt;Product Name='product' Id='9f6edf70-539a-11e4-916c-0800200c9a66' UpgradeCode='bb651370-539a-11e4-916c-0800200c9a66'
          Language='1033' Codepage='1252' Version='1.0.0' Manufacturer='Test'&gt;
          &lt;Package Id='*' Description="A product" InstallerVersion='301' Languages='1033'       Compressed='yes' SummaryCodepage='1252' Platform='x64'/&gt;
  
          &lt;Media Id="1" Cabinet="product.cab" EmbedCab="yes" /&gt;
  
          &lt;Directory Id='TARGETDIR' Name='SourceDir'&gt;
              &lt;Directory Id='ProgramFilesFolder'/&gt;
          &lt;/Directory&gt;
  
          &lt;Feature Id="Files" Title="Main Feature" Level="1"&gt;
              &lt;ComponentGroupRef Id="heatComponent"/&gt;
          &lt;/Feature&gt;
      &lt;/Product&gt;
  &lt;/Wix&gt;
  </code></pre>
  
  <p>But how do I do reference the ComponentGroup when I want to output a merge module? If I change the Product element to a Module element it complaints about the Feature element. If I remove that it works, but I do not get any files in my msm.</p>