title: Cmake: Create directory command in suddirectory's CMakeLists.txt file
body: <p>I have included a subdirectory in root's CMakeLists.txt with explicitly specifying the <code>binary_dir</code> as follow</p>
  
  <p><code>add_subdirectory(subdir_with_CMakeLists.txt out_dir)</code></p>
  
  <p>all the target are built into the <code>out_dir</code> as it supposed to, however <strong>MAKE_DIRECTORY</strong> command - <code>file(MAKE_DIRECTORY some_dir)</code> inside the included CMakeLists.txt creates the directory relative to the location of subdirectory's CMakeLists.txt, not inside the <code>out_dir</code> as I expected.</p>
  
  <p>Now, Is there a way to <strong>create a directory relative to the <code>binary_dir</code> specified in <code>add_subdirecoty</code> command?</strong>. </p>
  
  <p><strong>Note</strong>: The included subdirectory is a portable module so directory creation command should reside in its CMakeLists.txt file, not inside the root's CMakeLists.txt</p>