title: include_directory inheritance within CMake?
body: <p>I have 2 projects L and A in CMake, say L is a library and A an application depending on L.</p>
  
  <p>The folders hierarchy looks like:</p>
  
  <ul>
  <li>A
  
  <ul>
  <li>CMakeLists.txt + headers + src</li>
  </ul></li>
  <li>L
  
  <ul>
  <li>CMakeLists.txt + headers + src</li>
  <li>subL
  
  <ul>
  <li>headers + src files</li>
  </ul></li>
  </ul></li>
  </ul>
  
  <p>Now, in terms of include directories I understand I need to specify <strong>subL</strong> in <strong>L/CMakeLists.txt/include_directories()</strong>, so the other files within L can reference the include files simply with a <strong>#include "mySubLHeaderFile.h"</strong> or <strong>#include &lt; mySubLHeaderFile.h></strong>.</p>
  
  <p>Now if I want to reference a header file from <strong>subL</strong> within a file from the <strong>A</strong> project and be able to reference this <strong>subL</strong> file simply with a <strong>#include "mySubLHeaderFile.h"</strong> or <strong>#include &lt; mySubLHeaderFile.h></strong>, I have noticed I need to re-specify <strong>subL</strong> in <strong>A/CMakeLists.txt/include_directories()</strong>. Is this a normal behavior? Aren't the <strong>include_directories()</strong> inherited from the depended project?</p>
  
  <p>------ EDIT 1 -------</p>
  
  <p>Note that I have a top level CMakeLists.txt above A and L.</p>