pybricks/util_mp/pb_obj_helper: add LTO hack to pb_assert_type()

For unknown reasons, GCC 10 LTO is optimizing out pb_assert_type()
(presumably because it thinks the function has no side effects as
noinline has no effect). The GCC recommended workaround for such issues
is to include and empty inline assembly statement to prevent the
function from being optimized out.

Fixes: pybricks/support#950

Author: dlech

CHANGELOG.md

@@ -10,9 +10,11 @@
 
 ### Fixed
 - Fixed `Light` controlling wrong ports on Move hub ([support#913]).
+- Fixed type checking optimized out on Move hub ([support#950]).
 
 [support#904]: https://github.com/pybricks/support/issues/904
 [support#913]: https://github.com/pybricks/support/issues/913
+[support#950]: https://github.com/pybricks/support/issues/950
 
 ## [3.2.2] - 2023-01-06
 

pybricks/util_mp/pb_obj_helper.c

@@ -123,6 +123,10 @@ mp_obj_t pb_obj_get_base_class_obj(mp_obj_t obj, const mp_obj_type_t *type) {
 void pb_assert_type(mp_obj_t obj, const mp_obj_type_t *type) {
     if (!mp_obj_is_type(obj, type)) {
         #if MICROPY_ERROR_REPORTING == MICROPY_ERROR_REPORTING_TERSE
+        // HACK: for some reason, GCC 10 LTO optimizes out pb_assert_type()
+        // in the terse case. By adding an empty inline assembly statement,
+        // we prevent the incorrect optimization.
+        __asm__ ("");
         mp_raise_TypeError(NULL);
         #else
         mp_raise_msg_varg(&mp_type_TypeError, MP_ERROR_TEXT("can't convert %s to %s"),