[stubs] Enable machine graph verification for CodeStubAssembler and friends by default in debug mode

test/cctest/test-accessor-assembler.cc

Index: test/cctest/test-accessor-assembler.cc
diff --git a/test/cctest/test-accessor-assembler.cc b/test/cctest/test-accessor-assembler.cc
index 13786cff5f62af1752227bd70955e37596d92e04..c129bbaf133b73b02eaef108dd8285105daf65cf 100644
--- a/test/cctest/test-accessor-assembler.cc
+++ b/test/cctest/test-accessor-assembler.cc
@@ -36,7 +36,7 @@ void TestStubCacheOffsetCalculation(StubCache::Table table) {
       CHECK_EQ(StubCache::kSecondary, table);
       result = m.StubCacheSecondaryOffsetForTesting(name, primary_offset);
     }
-    m.Return(m.SmiFromWord32(result));
+    m.Return(m.SmiTag(result));
   }
 
   Handle<Code> code = data.GenerateCode();