[Coroutines] Fix unused var warning in release build

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@279610 91177308-0d34-0410-b5e6-96231b3b80d8

Author: GorNishanov

lib/Transforms/Coroutines/CoroFrame.cpp

@@ -182,8 +182,8 @@ SuspendCrossingInfo::SuspendCrossingInfo(Function &F, coro::Shape &Shape)
   }
 
   // Iterate propagating consumes and kills until they stop changing
-  int Iteration = 0;
-
+  int Iteration = 0; (void)Iteration;
+  
   bool Changed;
   do {
     DEBUG(dbgs() << "iteration " << ++Iteration);