the use of
<span class="target" id="index-1-command:add_custom_command"></span><a class="reference internal" href="../command/add_custom_command.html#command:add_custom_command" title="add_custom_command"><code class="xref cmake cmake-command docutils literal notranslate"><span class="pre">add_custom_command()</span></code></a> SOURCE signatures.  The <code class="docutils literal notranslate"><span class="pre">NEW</span></code> behavior for this
policy is to issue an error if such a signature is used.</p>
