When "make check TEMP_CONFIG=<(echo break_me=on)" spawns a postmaster that
fails startup, we detect that with "pg_regress: postmaster did not respond
within 60 seconds". pg_regress has a kill(postmaster_pid, 0) intended to
detect this case faster. Since kill(ZOMBIE-PID, 0) succeeds[1], that test is
ineffective. The fix, attached, is to instead test waitpid(), like pg_ctl's
wait_for_postmaster() does.
[1] Search for "zombie" in
http://pubs.opengroup.org/onlinepubs/9699919799/functions/kill.html