refactor: lazy get_type_size_bytes call

ir/be/begnuas.c

@@ -934,13 +934,13 @@ static size_t get_initializer_size(const ir_initializer_t *initializer,
 static unsigned long compute_entity_size(ir_entity const *const entity)
 {
 	ir_type *const type = get_entity_type(entity);
-	unsigned long  size = get_type_size_bytes(type);
 	if (is_alias_entity(entity))
-		return size;
+		return get_type_size_bytes(type);
 
 	/* Note that for variable array/compound types we may have to inspect the
 	 * initializer to get the actual size */
 	ir_initializer_t const *const initializer = get_entity_initializer(entity);
+	unsigned long size = 0;
 	if (initializer != NULL)
 		size = get_initializer_size(initializer, type);
 	return size;