compile.c: adjust label reference

* compile.c (new_adjust_body): labels referred by adjuststack
  shoud not be optimized away.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@53367 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

compile.c

@@ -989,6 +989,7 @@ new_adjust_body(rb_iseq_t *iseq, LABEL *label, int line)
     adjust->link.next = 0;
     adjust->label = label;
     adjust->line_no = line;
+    if (label) LABEL_REF(label);
     return adjust;
 }