[ocaml5-issue] Assertion failure in the debug runtime on STM int ref test

[shym]

In a CI log we have seen an assertion failure in the debug runtime for 5.1~rc1:

random seed: 465451623
generated error fail pass / total     time test name

[ ]    0    0    0    0 / 1000     0.0s STM int ref test parallel
[02] file runtime/domain.c; line 1001 ### Assertion failed: di->backup_thread_msg == BT_INIT || di->backup_thread_msg == BT_TERMINATE
File "src/neg_tests/dune", line 19, characters 7-27:
19 |  (name stm_tests_domain_ref)
            ^^^^^^^^^^^^^^^^^^^^
(cd _build/default/src/neg_tests && ./stm_tests_domain_ref.exe --verbose)
Command got signal ABRT.

It looks a lot like ocaml/ocaml#11800.

[jmid]

Fixed in ocaml/ocaml#12707