title: how to use #ifdef with an OR condition?
body: <p>Sorry for asking very basic question. I would like to set OR condition in #ifdef directive.?
  How to do that ?
  I tried</p>
  
  <pre><code>#ifdef LINUX | ANDROID
  ...
  ..
  #endif 
  </code></pre>
  
  <p>It did not work? What is the proper way?</p>