Fix custom validators call in build_local_reloptions()

We need to call them only when validate == true.

Backpatch to 13, where opclass options were introduced.

Reported-by: Tom Lane
Discussion: https://postgr.es/m/2656633.1681831542%40sss.pgh.pa.us
Reviewed-by: Tom Lane, Pavel Borisov
Backpatch-through: 13

src/backend/access/common/reloptions.c

@@ -1963,8 +1963,9 @@ build_local_reloptions(local_relopts *relopts, Datum options, bool validate)
 	fillRelOptions(opts, relopts->relopt_struct_size, vals, noptions, validate,
 				   elems, noptions);
 
-	foreach(lc, relopts->validators)
-		((relopts_validator) lfirst(lc)) (opts, vals, noptions);
+	if (validate)
+		foreach(lc, relopts->validators)
+			((relopts_validator) lfirst(lc)) (opts, vals, noptions);
 
 	if (elems)
 		pfree(elems);