Fixing arena chunk reuse.

src/alloy/hir/hir_builder.cc

@@ -72,6 +72,7 @@ int HIRBuilder::Finalize() {
         // Sometimes VC++ generates functions with bl at the end even if they
         // will never return. Just add a return to satisfy things.
         XELOGW("Fall-through out of the function.");
+        Trap();
         Return();
         current_block_ = NULL;
         break;