Fix -Werror build after r213945

llvm-svn: 213946
diff --git a/llvm/lib/IR/UseListOrder.cpp b/llvm/lib/IR/UseListOrder.cpp
index 42398ba..c1d3561 100644
--- a/llvm/lib/IR/UseListOrder.cpp
+++ b/llvm/lib/IR/UseListOrder.cpp
@@ -170,6 +170,7 @@
   SmallVector<char, 64> Vector;
   DEBUG(dbgs() << " - create-temp-file\n");
   if (auto EC = sys::fs::createTemporaryFile("use-list-order", Ext, Vector)) {
+    (void)EC;
     DEBUG(dbgs() << "error: " << EC.message() << "\n");
     return true;
   }