Fix the NDEBUG build

llvm-svn: 271411
diff --git a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
index c06cf2c..dec6770 100644
--- a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
@@ -932,6 +932,7 @@
   TypeIndex TI = lowerType(Ty);
 
   auto InsertResult = TypeIndices.insert({Ty, TI});
+  (void)InsertResult;
   assert(InsertResult.second && "DIType lowered twice");
   return TI;
 }