title: cmake install: how to remove subdir prefix
body: <p>I have a library libA. Structure is the following:</p>
  
  <pre><code>libA
  + CMakeLists.txt
  + mySRC/headerA.h
  + mySRC/headerB.h
  + mySRC/moduleA/modA.h
  + mySRC/moduleB/modB.h
  </code></pre>
  
  <p>My lib compiles fine and afterwards I want to install it using this cmake code:</p>
  
  <pre><code>SET(Source_dir mySRC)
  SET(LIB_NAME libA) 
  ...
  INSTALL(TARGETS ${LIB_NAME} DESTINATION /usr/local/lib)
  INSTALL(DIRECTORY ${Source_dir} 
  DESTINATION /usr/local/include/libA
  FILES_MATCHING PATTERN "*.h")
  </code></pre>
  
  <p><strong>Result:</strong></p>
  
  <p>libA.a ends up in</p>
  
  <pre><code>/usr/local/lib/libA.a (which is fine)
  </code></pre>
  
  <p>Headers end up in</p>
  
  <pre><code>/usr/local/include/libA/mySRC/*
  /usr/local/include/libA/mySRC/moduleA
  /usr/local/include/libA/mySRC/moduleB
  </code></pre>
  
  <p>What is not what I wanted. <strong>I want to remove "mySRC":</strong></p>
  
  <pre><code>/usr/local/include/libA/*
  /usr/local/include/libA/moduleA
  /usr/local/include/libA/moduleB
  </code></pre>
  
  <p>How can I remove mySRC from the path?</p>