8287749: Re-enable javadoc -serialwarn option

Reviewed-by: erikj

make/Docs.gmk

@@ -98,14 +98,14 @@ JAVA_WARNINGS_ARE_ERRORS ?= -Werror
 
 # The initial set of options for javadoc
 JAVADOC_OPTIONS := -use -keywords -notimestamp \
-    -encoding ISO-8859-1 -docencoding UTF-8 -breakiterator \
+    -serialwarn -encoding ISO-8859-1 -docencoding UTF-8 -breakiterator \
     -splitIndex --system none -javafx --expand-requires transitive \
     --override-methods=summary
 
 # The reference options must stay stable to allow for comparisons across the
 # development cycle.
 REFERENCE_OPTIONS := -XDignore.symbol.file=true -use -keywords -notimestamp \
-    -encoding ISO-8859-1 -breakiterator -splitIndex --system none \
+    -serialwarn -encoding ISO-8859-1 -breakiterator -splitIndex --system none \
     -html5 -javafx --expand-requires transitive
 
 # Should we add DRAFT stamps to the generated javadoc?

make/scripts/genExceptions.sh

@@ -1,6 +1,6 @@
 #! /bin/sh
 #
-# Copyright (c) 2000, 2021, Oracle and/or its affiliates. All rights reserved.
+# Copyright (c) 2000, 2025, Oracle and/or its affiliates. All rights reserved.
 # DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 #
 # This code is free software; you can redistribute it and/or modify it
@@ -70,6 +70,8 @@ __END__
 
     /**
      * The $ARG_PHRASE.
+     *
+     * @serial
      */
     private $ARG_TYPE $ARG_ID;