Fix typo in time passes

Summary:
Previously NamedRegionTimer's constructor was being called
with no local variable associated with it owing to a typo. We need a
local variable to keep track of the time spent in the scope. At the
end of the scope, the destructor will be called an then the timer will
stop.

(cherry picked from FBD4301844)

bolt/BinaryPassManager.cpp

@@ -156,7 +156,7 @@ void BinaryFunctionPassManager::runPasses() {
 
     auto &Pass = OptPassPair.second;
 
-    NamedRegionTimer(Pass->getName(), TimerGroupName, TimeOpts);
+    NamedRegionTimer T(Pass->getName(), TimerGroupName, TimeOpts);
 
     callWithDynoStats(
       [this,&Pass] {