include(CheckCXXCompilerFlag)

macro (append_compile_flag _flag)
    string (MAKE_C_IDENTIFIER ${_flag} _name)

    if (NOT __append_compile_flag_${_name})
        check_cxx_compiler_flag (${_flag} __append_compile_flag_${_name})
        if (__append_compile_flag_${_name})
            set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${_flag}")
            set (__append_compile_flag_${_name} 1 INTERNAL)
        endif ()
    endif ()
endmacro(append_compile_flag)