title: CMAKE string comparison fails
body: <p>I want to optionally add some library paths in my CMakeLists file and the way to do it to is to have a variable set as: </p>
  
  <pre><code>set(MYLIBDIR "DEFAULT")
  </code></pre>
  
  <p>If the user wants to specify a custom directory he will change it to:</p>
  
  <pre><code>set(MYLIBDIR /path/to/dir1
  /path/to/dir2)
  </code></pre>
  
  <p>So in order to check if the user has indeed provided extra directories I check:</p>
  
  <pre><code>if(NOT ${MYLIBDIR} STREQUAL "DEFAULT")
   link_directories(${MYLIBDIR})
  endif()
  </code></pre>
  
  <p>When I try to do this I am getting an error from cmake.
  Is there a way to concatenate all of the elements of a variable before the string comparison?</p>