title: CMake: setting the TARGET_FILE generator expression of a custom target
body: <p>I have a custom target. How do I set it's <code>TARGET_FILE</code> generator expression.</p>
  <pre><code>add_custom_target(my_target)
  ...
  # set TARGET_FILE
  ...
  # Use $&lt;TARGET_FILE:my_target&gt;
  </code></pre>
  <p>I tried to set the <code>LOCATION</code> target property hoping that then the <code>TARGET_FILE</code> generator expression would point to it, but that is not the case.</p>