title: Capture the requested parallel jobs in CMake
body: <p>Is it possible to capture the user-specified number of parallel build jobs with the <code>--parallel/-j</code> options in CMake?</p>
  
  <p>I realise you can specify this in CMake with <a href="https://cmake.org/cmake/help/latest/envvar/CMAKE_BUILD_PARALLEL_LEVEL.html#envvar:CMAKE_BUILD_PARALLEL_LEVEL" rel="nofollow noreferrer"><code>CMAKE_BUILD_PARALLEL_LEVEL</code></a>, but I am wondering how I can access the user's requested number within my CMake file.</p>