Mark a subsystem as dummy, not disabled, if it was intended to be compiled in.

From Tom Black:

I'm having problems initializing the sensor module. I'm compiling with a standard ./configure && make && sudo make install, and the module says it's enabled, but SDL_Init(SDL_INIT_EVERYTHING) is failing with SDL_GetError() returning "SDL not built with sensor support".

CMakeLists.txt

@@ -1565,7 +1565,7 @@ endif()
 # This leads to missing internal references on building, since the
 # src/X/*.c does not get included.
 if(NOT HAVE_SDL_JOYSTICK)
-  set(SDL_JOYSTICK_DISABLED 1)
+  set(SDL_JOYSTICK_DUMMY 1)
   if(SDL_JOYSTICK AND NOT APPLE) # results in unresolved symbols on OSX
 
     file(GLOB JOYSTICK_SOURCES ${SDL2_SOURCE_DIR}/src/joystick/dummy/*.c)
@@ -1573,10 +1573,15 @@ if(NOT HAVE_SDL_JOYSTICK)
   endif()
 endif()
 if(NOT HAVE_SDL_HAPTIC)
-  set(SDL_HAPTIC_DISABLED 1)
+  set(SDL_HAPTIC_DUMMY 1)
   file(GLOB HAPTIC_SOURCES ${SDL2_SOURCE_DIR}/src/haptic/dummy/*.c)
   set(SOURCE_FILES ${SOURCE_FILES} ${HAPTIC_SOURCES})
 endif()
+if(NOT HAVE_SDL_SENSORS)
+  set(SDL_SENSOR_DUMMY 1)
+  file(GLOB SENSORS_SOURCES ${SDL2_SOURCE_DIR}/src/sensor/dummy/*.c)
+  set(SOURCE_FILES ${SOURCE_FILES} ${SENSORS_SOURCES})
+endif()
 if(NOT HAVE_SDL_LOADSO)
   set(SDL_LOADSO_DISABLED 1)
   file(GLOB LOADSO_SOURCES ${SDL2_SOURCE_DIR}/src/loadso/dummy/*.c)
@@ -1587,11 +1592,6 @@ if(NOT HAVE_SDL_FILESYSTEM)
   file(GLOB FILESYSTEM_SOURCES ${SDL2_SOURCE_DIR}/src/filesystem/dummy/*.c)
   set(SOURCE_FILES ${SOURCE_FILES} ${FILESYSTEM_SOURCES})
 endif()
-if(NOT HAVE_SDL_SENSORS)
-  set(SDL_SENSOR_DISABLED 1)
-  file(GLOB SENSORS_SOURCES ${SDL2_SOURCE_DIR}/src/sensor/dummy/*.c)
-  set(SOURCE_FILES ${SOURCE_FILES} ${SENSORS_SOURCES})
-endif()
 
 # We always need to have threads and timers around
 if(NOT HAVE_SDL_THREADS)