SDL: Use bundled LibUSB when desirable

Previously, SDL would `find_package(libusb)` which would actually overwrite the user preference in the case where both USE_SYSTEM_LIBUSB and USE_SYSTEM_SDL were OFF. This coincidentally also allows SDL to use libusb on Windows.

Externals/SDL/CMakeLists.txt

@@ -20,6 +20,11 @@ if(CCACHE_BIN)
   set(CCACHE_BINARY ${CCACHE_BIN})
 endif()
 
+if(LibUSB_TYPE STREQUAL Bundled)
+  set(LibUSB_FOUND TRUE)
+  set(SDL_HIDAPI_LIBUSB_SHARED OFF)
+endif()
+
 add_subdirectory(SDL)
 
 if (TARGET SDL3)