title: Create Visual Studio "Custom Build Step" with CMake
body: <p>I would like to run a code generator every time my project is built in Visual Studio, even if no source file in the project was changed. Therefore I would like to have a custom build step set up as explained in <a href="https://stackoverflow.com/questions/1937702/visual-studio-run-c-project-post-build-event-even-if-project-is-up-to-date">Visual Studio: Run C++ project Post-Build Event even if project is up-to-date</a>.</p>
  
  <p>How can I create such a build step with CMake?</p>