title: heat generated files are not able to find SourceDir directory
body: <p>I am running heat to generate a wxs file. The code are as follows.</p>
  
  <p>I want to add all the files from dir.prompts to the wxs file in the installer. And I added this to be a part of the automated build process ( so that I cant modify the wxs file once it has been generated). </p>
  
  <p>The wxs file is generated, and it looks something like the following. Hoewever, then Light complains it can not find where SourceDir\Valid.wav is. So I guess my question is, is SourceDir the directory that I am reading the files from, or some magic directory that i am not aware of? Many thanks.</p>
  
  <pre><code> &lt;Fragment&gt;
      &lt;ComponentGroup Id="COMPONENTS"&gt;
          &lt;Component Id="dmp120F8C2794******" Directory="dir31A7EE61C56025FE2564A81E28E8C132" Guid="{6D40EBC0-***-***-B972-**********}"&gt;
              &lt;File Id="fil919100C2******D045EC131" KeyPath="yes" Source="SourceDir\Valid.wav" /&gt;
          &lt;/Component&gt;
  
  
  
  &lt;exec program ="${dir.wix}\heat.exe"&gt;
    &lt;arg value = "dir"/&gt;
    &lt;arg line = "${dir.prompts}"/&gt; 
    &lt;arg value= "-gg"/&gt;
    &lt;arg line="-cg &amp;quot;COMPONENTS&amp;quot;"/&gt;
    &lt;arg line = "-out  &amp;quot;${dir.thisinstaller}\\COMPONENTS.wxs&amp;quot;"/&gt; 
  &lt;/exec&gt;
  </code></pre>