rt: Add some debug code (ifdef'd out) for diagnosing marking problems

src/rt/rust_cc.cpp

@@ -176,6 +176,12 @@ irc::compute_ircs(rust_task *task, irc_map &ircs) {
                 ircs);
         irc.walk();
 
+#if 0
+        shape::log log(task, true, tydesc->shape, params, tydesc->shape_tables,
+                       p, std::cerr);
+        log.walk();
+#endif
+
         ++begin;
     }
 }