Don't enable D-Bus on Windows/OSX by default

Really not sure how the option logic is supposed to work. But currently
it will try to enable the QtDBus module on any OS.

CMakeLists.txt

@@ -19,7 +19,7 @@ set(CMAKE_EXPORT_COMPILE_COMMANDS ON CACHE BOOL "" FORCE)
 option(OPENELEC "Make an OpenELEC build" OFF)
 option(LINUX_X11POWER "Enable non D-Bus screensaver management" OFF)
 
-if(NOT LINUX_X11POWER)
+if((NOT LINUX_X11POWER) AND (UNIX AND (NOT APPLE)))
   set(LINUX_DBUS ON)
 endif()