s a command to generate specified <code class="docutils literal notranslate"><span class="pre">OUTPUT</span></code> file(s).
A target created in the same directory (<code class="docutils literal notranslate"><span class="pre">CMakeLists.txt</span></code> file)
that specifies any output of the custom command as a source file
is given a rule to generate the file using the command at build time.
Do not list the output in more than one independent target that
may build in parallel or the two instances of the ru