title: CMAKE with ROS to create external projects locally?
body: <p>I am working with ROS and wanted to modify the ardrone driver of autonomy lab. Unfortunately I have problems to build external libraries with CMake.
  The problem is following:</p>
  
  <p>The compiling original CMakeLists includes an external project:</p>
  
  <pre><code>include(ExternalProject)
  ExternalProject_Add(ardronelib
      GIT_REPOSITORY git://github.com/AutonomyLab/ardronelib.git
      GIT_TAG 2f987029c55531e4c0119c3600f9c57f935851ed
      PREFIX ${CATKIN_DEVEL_PREFIX}
      CONFIGURE_COMMAND echo "No configure"
      BUILD_COMMAND make
      INSTALL_COMMAND make install INSTALL_PREFIX=${CATKIN_DEVEL_PREFIX}/lib/
      BUILD_IN_SOURCE 1
  ) 
  </code></pre>
  
  <p>To modify this package, I downloaded it into my sourcefolder:</p>
  
  <pre><code>catkin_ws/src/my_project/
                           ardronelib/
                           src/ ...
                           launch/ ...
  ...
  </code></pre>
  
  <p>the ardronelib folder contains the makefile of the downloaded git project.</p>
  
  <pre><code>ardronelib/
             ARDroneLib
             .git
             .travis.yml
             LICENSE
             Makefile
             README.md
  </code></pre>
  
  <p>Basically I want to have the same libraries installed and linked as in the original version, but from this local folder.
  My approach with:</p>
  
  <pre><code>include(ExternalProject)
  ExternalProject_Add(ardronelib
      SOURCE_DIR=${PROJECT_SOURCE_DIR}/ardronelib
      PREFIX ${CATKIN_DEVEL_PREFIX}
      CONFIGURE_COMMAND echo "No configure"
      BUILD_COMMAND make
      INSTALL_COMMAND make install INSTALL_PREFIX=${CATKIN_DEVEL_PREFIX}/lib/
      BUILD_IN_SOURCE 1
  ) 
  </code></pre>
  
  <p>and several other attempts didn't work. Any ideas how to build the project so that later I can use the locally build "ardronelib" within my project?
  As the library is quite complex, the direct linking of the source files 
  would be to costly. Any ideas how I can use the same build structure, but instead of </p>
  
  <blockquote>
  <pre><code>    GIT_REPOSITORY git://github.com/AutonomyLab/ardronelib.git
      GIT_TAG 2f987029c55531e4c0119c3600f9c57f935851ed
  </code></pre>
  </blockquote>
  
  <p>us the local version:</p>
  
  <blockquote>
  <pre><code>    ${PROJECT_SOURCE_DIR}/ardronelib
  </code></pre>
  </blockquote>
  
  <p>I would be reaaally happy for any clues.
  Thanks a lot in advance!</p>