gtestutils: Set coredump rlimit to 0 when calling g_test_trap_fork()

g_test_trap_fork() is deprecated, but it’s still tested in the GLib
tests. If we don’t set the coredump rlimit to 0 to prevent coredumps,
the test for it creates a coredump (which is expected). On systems with
systemd-coredump, that causes systemd-coredump to spawn and process the
coredump for a while. That slows down the tests, and results in spurious
coredump lists in the system logs.

Signed-off-by: Philip Withnall <withnall@endlessm.com>

Fixes: #436

glib/gtestutils.c

@@ -3311,6 +3311,18 @@ g_test_trap_fork (guint64        usec_timeout,
         close (stdout_pipe[1]);
       if (stderr_pipe[1] >= 3)
         close (stderr_pipe[1]);
+
+      /* We typically expect these child processes to crash, and some
+       * tests spawn a *lot* of them.  Avoid spamming system crash
+       * collection programs such as systemd-coredump and abrt.
+       */
+#ifdef HAVE_SYS_RESOURCE_H
+      {
+        struct rlimit limit = { 0, 0 };
+        (void) setrlimit (RLIMIT_CORE, &limit);
+      }
+#endif
+
       return TRUE;
     }
   else                          /* parent */