CMAKE_HOST_SYSTEMΒΆ
Composite Name of OS CMake is being run on.
This variable is the composite of CMAKE_HOST_SYSTEM_NAME and
CMAKE_HOST_SYSTEM_VERSION, e.g.
${CMAKE_HOST_SYSTEM_NAME}-${CMAKE_HOST_SYSTEM_VERSION}. If
CMAKE_HOST_SYSTEM_VERSION is not set, then this variable is
the same as CMAKE_HOST_SYSTEM_NAME.