Add Boost on the include and link path.

It was only done when the auto-build was triggered, resulting in build errors
when Boost is available on the system but not on the standard paths.

modules/boost/boost.cmake

@@ -150,10 +150,10 @@ if(BUILD_CUSTOM_BOOST)
         list(APPEND Boost_LIBRARIES ${Boost_${_COMP}_LIBRARY})
     endforeach()
     set(Boost_INCLUDE_DIRS ${Boost_INCLUDE_DIR})
-    include_directories(SYSTEM ${Boost_INCLUDE_DIRS})
     set(Boost_LIBRARY_DIRS ${Boost_LIBRARY_DIR})
     if(CMAKE_SYSTEM_NAME MATCHES "Linux")
         list(APPEND Boost_LIBRARIES rt)
     endif()
-    link_directories(${Boost_LIBRARY_DIRS})
 endif(BUILD_CUSTOM_BOOST)
+include_directories(SYSTEM ${Boost_INCLUDE_DIRS})
+link_directories(${Boost_LIBRARY_DIRS})