fix -Werror build issue.

GitOrigin-RevId: 807a8daf1b2eaf251ac121bfc14e4537a0422026
diff --git a/include/flang/Optimizer/Dialect/FIROps.td b/include/flang/Optimizer/Dialect/FIROps.td
index 6bfbecc..a863e5e 100644
--- a/include/flang/Optimizer/Dialect/FIROps.td
+++ b/include/flang/Optimizer/Dialect/FIROps.td
@@ -1081,7 +1081,7 @@
       // Ok. If there is no dims and no layout map, then emboxing a scalar.
       // TODO: Should the type be enforced? It already must agree.
     } else if (dims().size() == 1) {
-      auto d = *dims().begin();
+      //auto d = *dims().begin();
     } else {
       return emitOpError("embox can only have one !fir.dim argument");
     }