MT#62787 Ensure grml-debootstrap's GRUB device is set also in SW-RAID setups

Since grml-debootstrap v0.116 there's a reworked GRUB setup, to support
installing both BIOS and UEFI bootloaders, and manage its updates via
grub-cloud-amd64 (see
2891f1730f
for details).

Now that we're shipping grml-debootstrap v0.119 in our latest
Grml-Sipwise deployment ISO, we're making use of its new behavior.

As it turned out, when deploying a SW-RAID based NGCP system, we invoke
grml-debootstrap with incomplete `--grub /dev/`. This is of course
incomplete and unexpected, but only started to fail with the more recent
grml-debootstrap version.

The underlying issue is grml-debootstrap setting GRUB's debconf
configuration to:

  grub-cloud-amd64/install_devices: /dev/

And if we're installing grub-cloud-amd64 (or its not an EFI system),
then grml-debootstrap also executes:

  grub-install --no-floppy --target=i386-pc "${device}"

Which of course won't work with the device being set to `/dev/`:

| Setting up grub-cloud-amd64 (0.0.5) ...
| Skipping installation without enable flag for cloud.
| Processing triggers for libc-bin (2.36-9+deb12u10) ...
| Installing grub on /dev/:
| Installing for x86_64-efi platform.
| Installation finished. No error reported.
| Installing for i386-pc platform.
| grub-install: error: cannot read `/dev': Is a directory.
| Error: failed to execute 'grub-install --no-floppy --target=i386-pc /dev/'.

To avoid any such failure, make sure grml-debootstrap's --grub option
uses a valid block device, also when installing SW-RAID (and even if it
actually shouldn't matter for EFI environments).

See https://github.com/grml/grml-debootstrap/issues/339 for further
details.

Change-Id: I6b839f708806c5107a1c86adbee1407cbeadddcc

templates/scripts/includes/deployment.sh

@@ -1822,10 +1822,14 @@ elif [[ -n "${SWRAID_DISK1}" ]] && [[ -n "${SWRAID_DISK2}" ]] ; then
 else
   [[ -z "${DISK}" ]] && die "Error: No non-removable disk suitable for installation found"
 fi
+
+# disk information and set GRUB target
 if [[ "${SWRAID}" = "true" ]] ; then
   DISK_INFO="Software-RAID with $SWRAID_DISK1 $SWRAID_DISK2"
+  GRUB_DISK="${SWRAID_DEVICE}"
 else
   DISK_INFO="/dev/$DISK"
+  GRUB_DISK="/dev/$DISK"
 fi
 
 ## detect environment {{{
@@ -2217,7 +2221,7 @@ debootstrap_sipwise_key
 # shellcheck disable=SC2086
 echo y | grml-debootstrap \
   --arch "${ARCH}" \
-  --grub "/dev/${DISK}" \
+  --grub "${GRUB_DISK}" \
   --filesystem "${FILESYSTEM}" \
   --hostname "${TARGET_HOSTNAME}" \
   --mirror "$MIRROR" \