if (UNIX)
    if (APPLE)
        set(WTF_OS_MAC_OS_X 1)
    else ()
        set(WTF_OS_UNIX 1)
    endif ()
elseif (CMAKE_SYSTEM_NAME MATCHES "Windows")
    set(WTF_OS_WINDOWS 1)
elseif (CMAKE_SYSTEM_NAME MATCHES "Fuchsia")
    set(WTF_OS_FUCHSIA 1)
else ()
    message(FATAL_ERROR "Unknown OS '${CMAKE_SYSTEM_NAME}'")
endif ()