For EC2, since you don't need core.img as I understand it, you should be able to preseed this:
grub-pc grub-pc/install_devices string grub-pc grub-pc/install_devices_empty boolean true
For EC2, since you don't need core.img as I understand it, you should be able to preseed this:
grub-pc grub-pc/ install_ devices string install_ devices_ empty boolean true
grub-pc grub-pc/