title: How to disable OpenMP directives in a nice way?
body: <p>I have C++ code with OpenMP pragmas inside. I want to test this code both for multithread mode (with OpenMP) and in single thread mode (no OpenMP). </p>
  
  <p>For now, to switch between modes I need to comment <code>#pragma omp</code> (or at least <code>parallel</code>).</p>
  
  <p>What is the cleanest, or default, way to enable / disable OpenMP?</p>