cmake：CheckCXXCompilerFlag

注意：必须先include(CheckCXXCompilerFlag)

例子1：在检查当前编译器是否支持c++11

CHECK_CXX_COMPILER_FLAG("-std=c++11" COMPILER_SUPPORTS_CXX11)
CHECK_CXX_COMPILER_FLAG("-std=c++0x"COMPILER_SUPPORTS_CXX0X)
if(COMPILER_SUPPORTS_CXX11)
  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
  add_definitions(-DCOMPILEDWITHC11)
  message(STATUS "Using flag -std=c++11.") 
elseif(COMPILER_SUPPORTS_CXX0X)
  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++0x")
  add_definitions(-DCOMPILEDWITHC0X)
  message(STATUS "Using flag -std=c++0x.")
else()
  message(FATAL_ERROR "The compiler ${CMAKE_CXX_COMPILER} has no C++11 support. Please use a different C++ compiler.")
endif()

例子2：避免二进制中的时间戳用于可复制构建，直到GCC 4.9才添加

include(CheckCXXCompilerFlag)
CHECK_CXX_COMPILER_FLAG(-Wdate-time COMPILER_SUPPORTS_WDATE_TIME)
if (COMPILER_SUPPORTS_WDATE_TIME)
    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wdate-time")
endif()

在4.9(含)的gcc版本中添加了-Wdate-time告警，如果在代码中使用了__DATE__, __TIME__, or __TIMESTAMP__这几个宏，会产生错误；