This means that `grub-install` and `update-grub` no longer risk
bricking the device, but will produce boot scripts with Mender support
integrated. It also means that the standard GRUB menu will be
available.
It is supported on x86_64 platforms where `grub.d` is available, and
can be turned on and off with `MENDER_GRUB_D_INTEGRATION`. The default
is to use it if available.
Devices that did not previously use `grub.d` integration won't be
upgraded correctly with it turned on, so it is advised to set
`MENDER_GRUB_D_INTEGRATION=n` if you are upgrading existing devices.
Changelog: Commit
Signed-off-by: Kristian Amlie <kristian.amlie@northern.tech>