fix: properly check for invalid argument in checkpkg and diffpkg

The option switch case only matches by splitting via '|' instead of ','

src/checkpkg.in

@@ -52,7 +52,7 @@ while (( $# )); do
 			shift
 			break
 			;;
-		-*,--*)
+		-*|--*)
 			die "invalid argument: %s" "$1"
 			;;
 		*)

src/diffpkg.in

@@ -129,7 +129,7 @@ while (( $# )); do
 			shift
 			break
 			;;
-		-*,--*)
+		-*|--*)
 			die "invalid argument: %s" "$1"
 			;;
 		*)