PGOPTIONS="-fh" make check gets stuck since Postgres 11

Hi all,

I have begun playing with regressplans.sh which enforces various
combinations of "-f s|i|n|m|h" when running the regression tests, and
I have noticed that -fh can cause the server to become stuck in the
test join_hash.sql with this query (not sure which portion of the SET
LOCAL parameters are involved) :
select count(*) from simple r join extremely_skewed s using (id);

This does not happen with REL_10_STABLE where the test executes
immediately, so we has visibly an issue caused by v11 here.

Any thoughts?
--
Michael