message: Update CMakeLists.txt
  This fixes the build errors that look like:
  source file is not valid
  This was due to CMake adding object files to the command line after the `-x` argument, which caused them to be interpreted as Objective C++ source code.
diff: @@ -127,7 +127,11 @@ endif()
  IF(MSVC)
  SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /EHsc")
  ELSEIF(APPLE)
  + if (CMAKE_CXX_COMPILER_ID MATCHES "Clang")
  + SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fobjc-arc -ObjC++")
  + ELSE()
  SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fobjc-arc -xobjective-c++")
  + ENDIF()
  ENDIF(MSVC)
  IF(WIN32)
  