title: C++ compile error when includeing Irrlicht static lib
body: <p>U have a compile error when trying to include the Irrlicht static libraries into my cmake project</p>
  
  <p>Compile error:</p>
  
  <pre>
  max@max-MS-7369:~/Desktop/survival/build$ make Scanning dependencies   of target survival
  [ 33%] Building CXX object    src/CMakeFiles/survival.dir/technic.cpp.o
  [ 66%] Building CXX object   src/CMakeFiles/survival.dir/render.cpp.o
  [100%] Building CXX object    src/CMakeFiles/survival.dir/survival.cpp.o
  Linking CXX executable    ../debug/survival
  /usr/bin/ld:    ../../irrlicht/lib/Linux/libIrrlicht.a(CIrrDeviceLinux.o): undefined   reference to symbol 'XConvertSelection'
  /usr/bin/ld: note:    'XConvertSelection' is defined in DSO    /usr/lib/gcc/x86_64-linux-gnu/4.6/../../../x86_64-linux-gnu/libX11.so  so try adding it to the linker command line
  /usr/lib/gcc/x86_64-linux-gnu/4.6/../../../x86_64-linux-gnu/libX11.so: could not read symbols: Invalid operation
  collect2: ld returned 1 exit status
  make[2]: *** [debug/survival] Error 1
  make[1]: ***    [src/CMakeFiles/survival.dir/all] Error 2
  make: *** [all] Error 2
  max@max-MS-7369:~/Desktop/survival/build$
  </pre>
  
  <p>And this is how I try to include the lib: </p>
  
  <pre>
  # find dependencies for irrlicht
  FIND_PACKAGE(ZLIB)
  FIND_PACKAGE(X11)
  FIND_PACKAGE(OpenGL)
  # includes
  set( survival_CUSTOM_INCLUDES
      ${ZLIB_INCLUDE_DIR}
      ${X11_INCLUDE_DIR}
      ${OPENGL_INCLUDE_DIR}
      ${survival_SOURCE_DIR}/irrlicht/include
      )
  # libraries
  set( survival_CUSTOM_LIBRARIES
      ${ZLIB_LIBRARIES}
      ${X11_LIBRARIES}
      ${OPENGL_LIBRARIES}
      ${survival_SOURCE_DIR}/irrlicht/lib/Linux/libIrrlicht.a
      )
  </pre>
  
  <p>I don't get why it says it cant find <code>XConvertSelection</code> even though I have included the X11 lib.</p>