sh: Properly show "Not a directory" error in cd builtin.

The errno message display added in r222292 did not take attempting to
cd to a non-directory or something that cannot be stat()ed into account.

PR:		bin/164070
MFC after:	10 days

bin/sh/cd.c

@@ -130,7 +130,12 @@ cdcmd(int argc, char **argv)
 	    (path = bltinlookup("CDPATH", 1)) == NULL)
 		path = nullstr;
 	while ((p = padvance(&path, dest)) != NULL) {
-		if (stat(p, &statb) >= 0 && S_ISDIR(statb.st_mode)) {
+		if (stat(p, &statb) < 0) {
+			if (errno != ENOENT)
+				errno1 = errno;
+		} else if (!S_ISDIR(statb.st_mode))
+			errno1 = ENOTDIR;
+		else {
 			if (!print) {
 				/*
 				 * XXX - rethink

tools/regression/bin/sh/builtins/cd8.0

@@ -0,0 +1,26 @@
+# $FreeBSD$
+
+# The exact wording of the error message is not standardized, but giving
+# a description of the errno is useful.
+
+LC_ALL=C
+export LC_ALL
+r=0
+
+t() {
+	exec 3>&1
+	errmsg=`cd "$1" 2>&1 >&3 3>&-`
+	exec 3>&-
+	case $errmsg in
+	*[Nn]ot\ a\ directory*)
+		;;
+	*)
+		printf "Wrong error message for %s: %s\n" "$1" "$errmsg"
+		r=3
+		;;
+	esac
+}
+
+t /dev/tty
+t /dev/tty/x
+exit $r