z/OS: signal(SIGPIPE, SIG_IGN) for tests

Updated:
   tests/testutil.hpp: Add signal(SIGPIPE, SIG_IGN) to
        setup_test_environment(), on z/OS (__MVS__)

tests/testutil.hpp

@@ -271,6 +271,11 @@ void setup_test_environment()
     // abort test after 60 seconds
     alarm(60);
 #endif
+#if defined __MVS__
+    // z/OS UNIX System Services: Ignore SIGPIPE during test runs, as a
+    // workaround for no SO_NOGSIGPIPE socket option.
+    signal(SIGPIPE, SIG_IGN);
+#endif
 }
 
 //  Provide portable millisecond sleep