Accept serialization of full builtins in noembed builds

In noembed builds we serialize all builtins as full on-heap code
objects.

Bug: v8:8716
Cq-Include-Trybots: luci.v8.try:v8_linux_noembed_rel_ng
Change-Id: I48f25a12e05a6d8599e5f9c31f9f56f2ebb9f2d6
Reviewed-on: https://chromium-review.googlesource.com/c/1448272Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59244}

src/snapshot/startup-serializer.cc

@@ -46,6 +46,7 @@ bool IsUnexpectedCodeObject(Isolate* isolate, HeapObject obj) {
 
   if (code->kind() == Code::REGEXP) return false;
   if (!code->is_builtin()) return true;
+  if (!FLAG_embedded_builtins) return false;
   if (code->is_off_heap_trampoline()) return false;
 
   // An on-heap builtin. We only expect this for the interpreter entry