py/persistentcode: Use MP_REGISTER_ROOT_POINTER().

This uses MP_REGISTER_ROOT_POINTER() to register track_reloc_code_list
instead of using a conditional inside of mp_state_vm_t.

Signed-off-by: David Lechner <david@pybricks.com>

py/mpstate.h

@@ -184,11 +184,6 @@ typedef struct _mp_state_vm_t {
     mp_obj_dict_t *mp_module_builtins_override_dict;
     #endif
 
-    #if MICROPY_PERSISTENT_CODE_TRACK_RELOC_CODE
-    // An mp_obj_list_t that tracks relocated native code to prevent the GC from reclaiming them.
-    mp_obj_t track_reloc_code_list;
-    #endif
-
     // Include any root pointers registered with MP_REGISTER_ROOT_POINTER().
     #ifndef NO_QSTR
     // Only include root pointer definitions when not doing qstr extraction, because

py/persistentcode.c

@@ -644,3 +644,8 @@ void mp_raw_code_save_file(mp_compiled_module_t *cm, const char *filename) {
 #endif // MICROPY_PERSISTENT_CODE_SAVE_FILE
 
 #endif // MICROPY_PERSISTENT_CODE_SAVE
+
+#if MICROPY_PERSISTENT_CODE_TRACK_RELOC_CODE
+// An mp_obj_list_t that tracks relocated native code to prevent the GC from reclaiming them.
+MP_REGISTER_ROOT_POINTER(mp_obj_t track_reloc_code_list);
+#endif