LP: #2034253 Grub is found to use lsb_release or default to Debian.
buildd does not have lsb_release, so Debian was the GRUB_DISTRIBUTION.
that ends up with issues with the EFI path
This now matches the cloud images (7c760864fdcb278ca37396f06f5e3f297428d63d)
fixing bootloader updates in the buildd images, but also fixing
compatibility with using devtmpfs for losetup.