[snapshot] Move builtins generation into mksnapshot

src/builtins/setup-builtins-deserialize.cc

+// Copyright 2017 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "src/builtins/setup-builtins.h"
+
+#include "src/base/logging.h"
+#include "src/isolate.h"
+
+namespace v8 {
+namespace internal {
+
+void SetupBuiltinsDelegate::SetupBuiltins(Isolate* isolate,
+                                          bool create_heap_objects) {
+  DCHECK(!create_heap_objects);
+  // No actual work to be done; builtins will be deserialized from the snapshot.
+  isolate->builtins()->MarkInitialized();
+}
+
+}  // namespace internal
+}  // namespace v8