I pointed a new custom domain to a Google App Engine Standard Environment project and edited the DNS records per Google\'s instructions, and it seems to be redirected proper
Ok for anyone still stuck on this:
Select Settings
Add custom domain. select your domain name. (if you have not verified your account before this then do that first)
Select the domain you want to add
you will get a list of things that you need to create in your hosting acount something like this:
if you bought your domain name in GoDaddy then you will have to go into your Godaddy account -> YourDomain.com -> DNS -> Manage Zones. Then enter it there thus:
go back to app engine and click verify.
Enjoy!