Per buildfarm members sungazer and mylodon. Back-patch to v15, which
introduced this test.
Discussion: https://postgr.es/m/
20220627070457.GA2176699@rfd.leadboat.com
# back to this timeline.
$node_pitr->safe_psql('postgres', "INSERT INTO foo VALUES(3);");
+# Wait for the archiver to be running. The startup process might have yet to
+# exit, in which case the postmaster has not started the archiver. If we
+# stop() without an archiver, the archive will be incomplete.
+$node_pitr->poll_query_until('postgres',
+ "SELECT true FROM pg_stat_activity WHERE backend_type = 'archiver';")
+ or die "Timed out while waiting for archiver to start";
+
# Stop the node. This archives the last segment.
$node_pitr->stop();