GRUB_EFI: arm64 grub EFI installation support

The "--target=x86_64-efi" option obviously does not work for arm64
installation. Skip it in case of an arm64 installation, the x86-64
default is unchanged.

NB: This work comes from the SEAPATH project:
seapath/build_debian_iso#121

Co-authored-by: Florent CARLI <florent.carli@rte-france.com>
Signed-off-by: Yoann Congal <yoann.congal@smile.fr>

scripts/GRUB_EFI/10-setup

@@ -46,7 +46,13 @@ if [ "${_bdev%%-*}" = "/dev/dm" ]; then
   BOOT_DEVICE=$( lvs --noheadings -o devices $BOOT_DEVICE | sed -e 's/^*\([^(]*\)(.*$/\1/' )
 fi
 
-opts="--no-floppy --target=x86_64-efi --modules=part_gpt"
+# ARM64 or AMD64
+arch=$(uname -m)
+if [ "$arch" == "aarch64" ]; then
+    opts="--no-floppy --modules=part_gpt"
+else
+    opts="--no-floppy --target=x86_64-efi --modules=part_gpt"
+fi
 
 # Check if RAID is used for the boot device
 if [[ $BOOT_DEVICE =~ '/dev/md' ]]; then