title: linking bullet include directory with cmake
body: <p>I have a common problem, "include not found". While I was using the command line to set the includes and libraries directories everything was fine,
  Quote:</p>
  
  <pre><code>g++ src/B_engine.cc -lLinearMath -lBulletSoftBody -lBulletCollision -lBulletDynamics -I/usr/include/bullet -o a.out
  </code></pre>
  
  <p>but I need to make it working with cmake, there is a copy of my current cmake,</p>
  
  <pre><code>cmake_minimum_required( VERSION 2.8 )
  project( a.out )
  set( SOURCES src/B_engine.cc )
  set( EXECUTABLE_NAME a.out )
  find_package( Bullet REQUIRED )
  add_executable( ${EXECUTABLE_NAME} ${SOURCES} )
  add_definitions(-std=c++11)
  </code></pre>
  
  <p>when I do a "ccmake .", I see :</p>
  
  <pre><code>BULLET_INCLUDE_DIR /usr/include/bullet
  CMAKE_BUILD_TYPE
  CMAKE_INSTALL_PREFIX /usr/local
  </code></pre>
  
  <p>so, me (with the command line) and cmake are expecting to use /usr/include/bullet as directory. But when I do "make", I get this error :</p>
  
  <pre><code>[100%]
  Scanning dependencies of target a.out
  Building CXX object CMakeFiles/a.out.dir/src/B_engine.cc.o
  In file included from /home/user/test/src/B_engine.cc:2:0:/home/user/test/src/B_engine.hh:5:36: fatal error: btBulletDynamicsCommon.h: No such file or directory
   #include &lt;btBulletDynamicsCommon.h&gt;
  </code></pre>
  
  <p>I do not understand why the g++ command line and cmake doesn't give the same result.</p>