title: MsBuild: Flattening of nested ItemGroup with variable number of metadata
body: <p>Assume the following ItemGroup structure:</p>
  
  <pre class="lang-xml prettyprint-override"><code>&lt;ItemGroup&gt;
    &lt;BinaryFiles Include="C:\"&gt;
      &lt;Binary&gt;a.dll&lt;/Binary&gt;
      &lt;Binary&gt;b.dll&lt;/Binary&gt;
    &lt;/BinaryFiles&gt;
    &lt;BinaryFiles Include="D:\"&gt;
      &lt;Binary&gt;my.ddl&lt;/Binary&gt;
    &lt;/BinaryFiles&gt;
  &lt;/ItemGroup&gt;
  </code></pre>
  
  <p>I need to flatten this to a string like this:</p>
  
  <pre><code>C:\a.dll;C:\b.dll;D:\my.dll
  </code></pre>
  
  <p>How would I do that? If it's not possible, is there a better way to do it?</p>