Fix migration from Barebox GRUB (#1767)

* Fix migration from Barebox GRUB

Create GRUB env which defaults to the boot slot we are updating to. This
makes sure that the newly installed OS version will be booted on next
reboot even if installed on boot slot B.

buildroot-external/ota/rauc-hook

@@ -54,6 +54,12 @@ if [ "${RAUC_SLOT_CLASS}" = "boot" ]; then
     # Update
     cp -rf "${BOOT_NEW}"/* "${BOOT_MNT}/"
 
+    # If grubenv is missing, initialize with boot order which will try the right
+    # boot slot
+    if [ -d "${BOOT_NEW}"/EFI/BOOT/ ] && [ ! -f "${BOOT_NEW}"/EFI/BOOT/grubenv ]; then
+        cp -f "${BOOT_NEW}/EFI/BOOT/grubenv-${RAUC_SLOT_BOOTNAME}" "${BOOT_NEW}"/EFI/BOOT/grubenv
+    fi
+
     # Restore boot config
     cp -f "${BOOT_TMP}"/*.txt "${BOOT_MNT}/"