Fix unexec compilation

* src/pdumper.c (thaw_hash_tables): Now conditioned by
HAVE_PDUMPER.
(init_pdumper_once): No-op unless HAVE_PDUMPER.  Reported by
Nikolay Kudryavtsev <nikolay.kudryavtsev@gmail.com>.

src/pdumper.c

@@ -5463,9 +5463,6 @@ Value is nil if this session was not started using a dump file.*/)
 		Fcons (Qdump_file_name, dump_fn));
 }
 
-#endif /* HAVE_PDUMPER */
-
-
 static void
 thaw_hash_tables (void)
 {
@@ -5474,10 +5471,15 @@ thaw_hash_tables (void)
     hash_table_thaw (AREF (hash_tables, i));
 }
 
+#endif /* HAVE_PDUMPER */
+
+
 void
 init_pdumper_once (void)
 {
+#ifdef HAVE_PDUMPER
   pdumper_do_now_and_after_load (thaw_hash_tables);
+#endif
 }
 
 void