[ssa-updater] Allow a user to set the InsertedPHIs list after construction.

I need this API so that I can conditionally handle the inserted phis.

Author: gottesmm

include/swift/SILOptimizer/Utils/SILSSAUpdater.h

@@ -63,6 +63,10 @@ class SILSSAUpdater {
       SmallVectorImpl<SILPhiArgument *> *InsertedPHIs = nullptr);
   ~SILSSAUpdater();
 
+  void setInsertedPhis(SmallVectorImpl<SILPhiArgument *> *insertedPhis) {
+    InsertedPHIs = insertedPhis;
+  }
+
   /// Initialize for a use of a value of type.
   void Initialize(SILType T);