If setting `CMAKE_CXX_STANDARD` doesn't work to get `-std=c++11` or `-std=gnu++11` into the CXX_FLAGS, then maybe the version of CMake is < 3.1.0?
The variable `CMAKE_CXX_STANDARD` was added to CMake in the capacity of setting (e.g.) `-std=c++11` as of CMake 3.1.0. The code would be something like:
{{{
# If cmake version is < 3.1, explicitly set C/C++ standard to use;
# this CMake doesn't internally use CMAKE_C*_STANDARD variables.
IF(${CMAKE_VERSION} VERSION_LESS 3.1)
SET(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -std=c${CMAKE_C_STANDARD}")
SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++${CMAKE_CXX_STANDARD}")
ENDIF()
}}}
Worth a try! - MLD