我尝试设置 CMAKE_C_FLAGS

I tried to set CMAKE_C_FLAGS

根据文档，CMAKE_C_FLAGS为所有构建类型设置 C 语言标志.对于 C++，您需要使用 CMAKE_CXX_FLAGS 代替:

According to the documentation the CMAKE_C_FLAGS set C language flags for all build types. For C++ you need use CMAKE_CXX_FLAGS instead:

set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")