skip a problematic test on openbsd/thread

I'd make this a TODO, but the test currently results in the watchdog
firing, so harness/TEST would never see the "TODO".

Author: tonycoz

t/op/sigdispatch.t

@@ -41,6 +41,8 @@ is($@, "Alarm!\n", 'after the second loop');
 SKIP: {
     skip('We can\'t test blocking without sigprocmask', 11)
 	if is_miniperl() || !$Config{d_sigprocmask};
+    skip('This doesn\'t work on OpenBSD threaded builds RT#88814', 11)
+        if $^O eq 'openbsd' && $Config{useithreads};
 
     require POSIX;
     my $new = POSIX::SigSet->new(&POSIX::SIGUSR1);