title: pugixml include dir set to not found from pugixml config cmake files
body: <p>I am trying to compile this project: <a href="https://github.com/computationalpathologygroup/ASAP.git" rel="nofollow noreferrer">https://github.com/computationalpathologygroup/ASAP.git</a> from source.
  Pugixml is a dependency</p>
  
  <p>I have built pugixml from source and set PugiXML_DIR and PUGIXML_INCLUDE_DIR And it still gives me error:  "CMake Error: The following variables are used in this project, but they are set to NOTFOUND."</p>
  
  <p><strong>Things I have tried</strong>:</p>
  
  <ul>
  <li>I am doing this on windows, using cmake 3.14 and visual studio 2017. </li>
  <li>I have successfully built pugixml from source and included the .lib file as well</li>
  <li>I have tried including and excluding combinations of PUGIXML_INCLUDE_DIR, PUGIXML_LIBRARY, PugiXML_DIR.</li>
  </ul>
  
  <p><strong>This is the error I get</strong>:</p>
  
  <pre><code>CMake Error: The following variables are used in this project, but they are set to NOTFOUND.
  Please set them or make sure they are set and tested correctly in the CMake files:
  cpp/ASAP/annotation/PUGIXML_INCLUDE_DIR
     used as include directory in directory 
  /cpp/ASAP/annotation
  cpp/ASAP/multiresolutionimageinterface/PUGIXML_INCLUDE_DIR
     used as include directory in directory cpp/ASAP/multiresolutionimageinterface
  </code></pre>
  
  <p><strong>Other information</strong>: setting PugiXML_DIR is mandatory, and the cmake looks for a file named "pugixml-config.cmake" in that directory. And the config cmake file is supposed to point to compiled lib file. But when it wasn't able to find, I simply copied the lib file I compiled to the location pugixml-config.cmake was pointing.  </p>