abuild: only update config.sub if our version is newer

and exit with error if not

abuild.in

@@ -573,10 +573,21 @@ mkusers() {
 
 # helper to update config.sub to a recent version
 update_config_sub() {
+	local myver=$("$datadir"/config.sub -t | tr -d '-')
+	local changed=false
 	find . -name config.sub | while read f; do
-		msg "Replacing ${f##*/}"
-		cp "$datadir"/${f##*/} "$f" || return 1
+		local ver=$(./"$f" -t | tr -d '-')
+		if [ "$myver" -gt "$ver" ]; then
+			msg "Updating $f ($myver > $ver)"
+			cp "$datadir"/${f##*/} "$f" || return 1
+			changed=true
+		else
+			msg "Not updating newer $f"
+		fi
+		# pipe subshell will return status of last command
+		$changed
 	done
+	return $?
 }
 
 runpart() {