title: Boost.Log with CMake causing undefined reference error
body: <p>I am trying to use the new Boost.Log library in a project I am working on. The project is built with CMake. I am receiving link errors claiming that the linker has come across undefined references to Boost.Log</p>
  
  <pre><code>Linking CXX executable main
  CMakeFiles/main.dir/main.cpp.o: In function `main':
  main.cpp:(.text+0x30): undefined reference to `boost::log::v2s_mt_posix::trivial::logger::get()'
  </code></pre>
  
  <p>I have a simple hello world test that fails with these errors. If I am linking against the Boost.Log libraries what would cause it to generate an undefined reference error?</p>
  
  <p>main.cpp:</p>
  
  <pre><code>#include &lt;boost/log/trivial.hpp&gt;
  int main(int argc, char* const argv[]) {
    BOOST_LOG_TRIVIAL(info) &lt;&lt; "Hello World";
  }
  </code></pre>
  
  <p>CMakeLists.txt:</p>
  
  <pre><code>CMAKE_MINIMUM_REQUIRED(VERSION 2.8)
  FIND_PACKAGE(Boost 1.54 COMPONENTS log REQUIRED)
  FIND_PACKAGE(Threads)
  INCLUDE_DIRECTORIES(${Boost_INCLUDE_DIR})
  ADD_EXECUTABLE(main main.cpp)
  TARGET_LINK_LIBRARIES(main ${Boost_LOG_LIBRARY} ${CMAKE_THREAD_LIBS_INIT})
  </code></pre>
  
  <p><strong>Edit: verbose output from cmake and make</strong></p>
  
  <p>cmake:</p>
  
  <pre><code>-- [ /usr/share/cmake-2.8/Modules/FindBoost.cmake:476 ] _boost_TEST_VERSIONS = 1.56.0;1.56;1.55.0;1.55;1.54.0;1.54
  -- [ /usr/share/cmake-2.8/Modules/FindBoost.cmake:478 ] Boost_USE_MULTITHREADED = TRUE
  -- [ /usr/share/cmake-2.8/Modules/FindBoost.cmake:480 ] Boost_USE_STATIC_LIBS = 
  -- [ /usr/share/cmake-2.8/Modules/FindBoost.cmake:482 ] Boost_USE_STATIC_RUNTIME = 
  -- [ /usr/share/cmake-2.8/Modules/FindBoost.cmake:484 ] Boost_ADDITIONAL_VERSIONS = 
  -- [ /usr/share/cmake-2.8/Modules/FindBoost.cmake:486 ] Boost_NO_SYSTEM_PATHS = 
  -- [ /usr/share/cmake-2.8/Modules/FindBoost.cmake:538 ] Declared as CMake or Environmental Variables:
  -- [ /usr/share/cmake-2.8/Modules/FindBoost.cmake:540 ]   BOOST_ROOT = 
  -- [ /usr/share/cmake-2.8/Modules/FindBoost.cmake:542 ]   BOOST_INCLUDEDIR = 
  -- [ /usr/share/cmake-2.8/Modules/FindBoost.cmake:544 ]   BOOST_LIBRARYDIR = 
  -- [ /usr/share/cmake-2.8/Modules/FindBoost.cmake:546 ] _boost_TEST_VERSIONS = 1.56.0;1.56;1.55.0;1.55;1.54.0;1.54
  -- [ /usr/share/cmake-2.8/Modules/FindBoost.cmake:639 ] location of version.hpp: /usr/include/boost/version.hpp
  -- [ /usr/share/cmake-2.8/Modules/FindBoost.cmake:663 ] version.hpp reveals boost 1.54.0
  -- [ /usr/share/cmake-2.8/Modules/FindBoost.cmake:739 ] guessed _boost_COMPILER = -gcc48
  -- [ /usr/share/cmake-2.8/Modules/FindBoost.cmake:749 ] _boost_MULTITHREADED = -mt
  -- [ /usr/share/cmake-2.8/Modules/FindBoost.cmake:792 ] _boost_RELEASE_ABI_TAG = -
  -- [ /usr/share/cmake-2.8/Modules/FindBoost.cmake:794 ] _boost_DEBUG_ABI_TAG = -d
  -- [ /usr/share/cmake-2.8/Modules/FindBoost.cmake:842 ] _boost_LIBRARY_SEARCH_DIRS = /usr/lib64;NO_DEFAULT_PATH
  -- [ /usr/share/cmake-2.8/Modules/FindBoost.cmake:930 ] Searching for LOG_LIBRARY_RELEASE: boost_log-gcc48-mt-1_54;boost_log-gcc48-mt;boost_log-mt-1_54;boost_log-mt;boost_log
  -- [ /usr/share/cmake-2.8/Modules/FindBoost.cmake:966 ] Searching for LOG_LIBRARY_DEBUG: boost_log-gcc48-mt-d-1_54;boost_log-gcc48-mt-d;boost_log-mt-d-1_54;boost_log-mt-d;boost_log-mt;boost_log
  -- [ /usr/share/cmake-2.8/Modules/FindBoost.cmake:1017 ] Boost_FOUND = 1
  -- Boost version: 1.54.0
  -- Found the following Boost libraries:
  --   log
  -- Configuring done
  -- Generating done
  -- Build files have been written to: /home/durrw/boost-log-test/build
  </code></pre>
  
  <p>make:</p>
  
  <pre><code>/usr/bin/cmake -H/home/durrw/boost-log-test -B/home/durrw/boost-log-test/build --check-build-system CMakeFiles/Makefile.cmake 0
  /usr/bin/cmake -E cmake_progress_start /home/durrw/boost-log-test/build/CMakeFiles /home/durrw/boost-log-test/build/CMakeFiles/progress.marks
  make -f CMakeFiles/Makefile2 all
  make[1]: Entering directory `/home/durrw/boost-log-test/build'
  make -f CMakeFiles/main.dir/build.make CMakeFiles/main.dir/depend
  make[2]: Entering directory `/home/durrw/boost-log-test/build'
  cd /home/durrw/boost-log-test/build &amp;&amp; /usr/bin/cmake -E cmake_depends "Unix Makefiles" /home/durrw/boost-log-test /home/durrw/boost-log-test /home/durrw/boost-log-test/build /home/durrw/boost-log-test/build /home/durrw/boost-log-test/build/CMakeFiles/main.dir/DependInfo.cmake --color=
  make[2]: Leaving directory `/home/durrw/boost-log-test/build'
  make -f CMakeFiles/main.dir/build.make CMakeFiles/main.dir/build
  make[2]: Entering directory `/home/durrw/boost-log-test/build'
  Linking CXX executable main
  /usr/bin/cmake -E cmake_link_script CMakeFiles/main.dir/link.txt --verbose=1
  /usr/bin/c++       CMakeFiles/main.dir/main.cpp.o  -o main -rdynamic -lboost_log -lpthread 
  CMakeFiles/main.dir/main.cpp.o: In function `main':
  main.cpp:(.text+0x39): undefined reference to `boost::log::v2s_mt_posix::trivial::logger::get()'
  </code></pre>