NANA_CMAKE_ENABLE_MINGW_STD_THREADS_WITH_MEGANZ option must still be enabled but mingw.thread.h and mingw.mutex.h will be ignored if _GLIBCXX_HAS_GTHREADS is defined
NANA_CMAKE_ENABLE_MINGW_STD_THREADS_WITH_MEGANZ option must still be enabled but mingw.thread.h and mingw.mutex.h will be ignored if _GLIBCXX_HAS_GTHREADS is defined