Serialize witnesses if -sil-serialize-witness-tables is provided

Author: swiftix

lib/SILGen/SILGenType.cpp

@@ -482,7 +482,9 @@ class SILGenConformance : public SILGenWitnessTable<SILGenConformance> {
     if (witnessSerialized &&
         fixmeWitnessHasLinkageThatNeedsToBePublic(witnessLinkage)) {
       witnessLinkage = SILLinkage::Public;
-      witnessSerialized = IsNotSerialized;
+      witnessSerialized = (SGM.M.getOptions().SILSerializeWitnessTables
+                           ? IsSerialized
+                           : IsNotSerialized);
     } else {
       // This is the "real" rule; the above case should go away once we
       // figure out what's going on.