Merge branch 'mnowak/warning-array-subscript-is-of-type-char-on-netbsd-9' into 'main'

Fix "array subscript is of type 'char'" on NetBSD 9

See merge request isc-projects/bind9!5591

lib/dns/rdata/in_1/svcb_64.c

@@ -256,7 +256,7 @@ svc_fromtext(isc_textregion_t *region, isc_buffer_t *target) {
 			RETERR(alpn_fromtxt(region, target));
 			break;
 		case sbpr_port:
-			if (!isdigit(*region->base)) {
+			if (!isdigit((unsigned char)*region->base)) {
 				return (DNS_R_SYNTAX);
 			}
 			ul = strtoul(region->base, &e, 10);