title: How to execute CMake's default find module from my own find module with the same name?
body: <p>For some reason I want to extend a find module (<code>FindThreads</code> in my case) to do some specific stuff if CMake's <code>FindThreads</code> fails. For the ordinary developer of other parts of our software system this should happen transparently, such that s/he could call <code>find_package(Threads)</code> as usual, so I don't want to give my own find module an exclusive name.</p>
  
  <p>My idea is to add my own <code>FindThreads.cmake</code> in a folder contained in the <code>CMAKE_MODULE_PATH</code>. Because <code>CMAKE_MODULE_PATH</code> has priority <code>find_package(Threads)</code> will execute my own <code>FindThreads.cmake</code>.</p>
  
  <p>But, inside my own <code>FindThreads.cmake</code> I need to execute <code>find_package(Threads ...)</code> such that it executes CMake's original <code>FindThreads.cmake</code>. <strong>How to do that?</strong></p>
  
  <p>If that fails my own <code>FindThreads.cmake</code> should try to add a specific Threads lib.</p>
  
  <p>Unfortunately, there is no option <code>NO_CMAKE_MODULE_PATH</code> for <code>find_package</code> to fall back to CMake's own find modules and it seems not to be possible to pass a search path (for example <code>${CMAKE_ROOT}/Modules</code>) to <code>find_package</code> to override <code>CMAKE_MODULE_PATH</code>.</p>
  
  <h2>Versions</h2>
  
  <ul>
  <li>CMake 3.5 on Linux (Ubuntu 16.04)</li>
  <li>CMake 3.14 on Windows</li>
  </ul>