cmake: fix typo's in last commit

CMakeLists.txt

@@ -203,9 +203,9 @@ elseif(NINTENDO_3DS)
   set(N3DS TRUE)
 endif()
 
-set(SDL_EXTRA_CHECK_INCLUDES "" CACHE STRING "Extra includes (for CMAKE_REQUIRED_INCLUDES)")
-set(SDL_EXTRA_CHECK_LINK_OPTIONS "" CACHE STRING "Extra link options (for CMAKE_REQUIRED_LINK_OPTIONS)")
-mark_as_advanced(SDL_EXTRA_CHECK_INCLUDES SDL_EXTRA_CHECK_LINK_OPTIONS)
+set(SDL_CHECK_REQUIRED_INCLUDES "" CACHE STRING "Extra includes (for CMAKE_REQUIRED_INCLUDES)")
+set(SDL_CHECK_REQUIRED_LINK_OPTIONS "" CACHE STRING "Extra link options (for CMAKE_REQUIRED_LINK_OPTIONS)")
+mark_as_advanced(SDL_CHECK_REQUIRED_INCLUDES SDL_CHECK_REQUIRED_LINK_OPTIONS)
 
 list(APPEND CMAKE_REQUIRED_INCLUDES ${SDL_CHECK_REQUIRED_INCLUDES})
 list(APPEND CMAKE_REQUIRED_LINK_OPTIONS ${SDL_CHECK_REQUIRED_LINK_OPTIONS})