Revert "Do not use arg.h for tools which take no flags"

This reverts commit 9016d288f1.

Tools that have no options are required by POSIX to support "--" so
that conforming applications have a way to shield their operands from
implementations that provide options as an extension.

echo(1) is just an exception, so it is handled specially.

See OPTIONS in https://pubs.opengroup.org/onlinepubs/9699919799.2018edition/utilities/V3_chap01.html#tag_17_04

yes.c

@@ -3,12 +3,21 @@
 
 #include "util.h"
 
+static void
+usage(void)
+{
+	eprintf("usage: %s [string ...]\n", argv0);
+}
+
 int
 main(int argc, char *argv[])
 {
 	char **p;
 
-	argv0 = *argv, argv0 ? (argc--, argv++) : (void *)0;
+	ARGBEGIN {
+	default:
+		usage();
+	} ARGEND
 
 	for (p = argv; ; p = (*p && *(p + 1)) ? p + 1 : argv) {
 		fputs(*p ? *p : "y", stdout);