It looks like the issue hasn’t been totally solved. You’ll have to use a program called rcedit in order to hack it in (see akien-mga’s comment near the bottom of the GitHub thread for more information).
Why did it not work? Sorry, I was on my mobile phone, and couldn’t give a proper response.
Ertain | 2018-02-09 18:27
Tested with both rceditx86 and x64, info was successfully changed, icon remained godot’s default. Icon was a proper .ico. Restarted the computer after to make sure. Just didn’t work.
And who downvoted me? I simply said it didn’t work… It’s not my fault, you know…