Fix -Wunused-variable in release build.

Author: hokein

llvm/lib/Transforms/IPO/OpenMPOpt.cpp

@@ -2414,8 +2414,7 @@ struct AAICVTrackerCallSite : AAICVTracker {
       : AAICVTracker(IRP, A) {}
 
   void initialize(Attributor &A) override {
-    Function *F = getAnchorScope();
-    assert(F && "Expected anchor function");
+    assert(getAnchorScope() && "Expected anchor function");
 
     // We only initialize this AA for getters, so we need to know which ICV it
     // gets.