IRGen: Emit reference to class stub from class context descriptor

This was an oversight. I was setting the flag but not emitting the
pointer at the end.

Author: slavapestov

lib/IRGen/GenMeta.cpp

@@ -1399,6 +1399,7 @@ namespace {
       super::layout();
       addVTable();
       addOverrideTable();
+      addObjCResilientClassStubInfo();
     }
 
     void addIncompleteMetadataOrRelocationFunction() {
@@ -1632,6 +1633,20 @@ namespace {
       // uint32_t FieldOffsetVectorOffset;
       B.addInt32(getFieldVectorOffset() / IGM.getPointerSize());
     }
+
+    void addObjCResilientClassStubInfo() {
+      if (IGM.getClassMetadataStrategy(getType()) !=
+            ClassMetadataStrategy::Resilient)
+        return;
+
+      if (!hasObjCResilientClassStub(IGM, getType()))
+        return;
+
+      B.addRelativeAddress(
+        IGM.getAddrOfObjCResilientClassStub(
+          getType(), NotForDefinition,
+          TypeMetadataAddress::AddressPoint));
+    }
   };
 
   class OpaqueTypeDescriptorBuilder

test/IRGen/class_update_callback_with_stub.swift

@@ -51,6 +51,8 @@ import resilient_objc_class
 // CHECK-SAME: @"got.$s15resilient_class22ResilientOutsideParentCMn"
 // CHECK-SAME: @"got.$s15resilient_class22ResilientOutsideParentCACycfCTq"
 // CHECK-SAME: @"$s31class_update_callback_with_stub17ResilientSubclassCACycfC"
+// -- class stub
+// CHECK-SAME: @"$s31class_update_callback_with_stub17ResilientSubclassCMt"
 // CHECK-SAME: }>, section "__TEXT,__const", align 4