Update build script to facilitate iso builds

Signed-off-by: Rahul Ganesh <rahulbabu95@gmail.com>

Author: rahulbabu95

bash/linuxkit.sh

@@ -100,6 +100,25 @@ function linuxkit_build() {
 	log info "Building Hook with kernel ${inventory_id} using linuxkit: ${lk_args[*]}"
 	"${linuxkit_bin}" build "--format" "kernel+initrd" "${lk_args[@]}"
 
+	# if LINUXKIT_ISO is set, build an ISO with the kernel and initramfs
+	if [[ -n "${LINUXKIT_ISO}" ]]; then
+		declare lk_iso_output_dir="out"
+		mkdir -p "${lk_iso_output_dir}"
+
+		declare -a lk_iso_args=(
+			"--docker"
+			"--arch" "${kernel_info['DOCKER_ARCH']}"
+			"--format" "iso-efi-initrd"
+			"--name" "hook"
+			"--cache" "${lk_cache_dir}"
+			"--dir" "${lk_iso_output_dir}"
+			"hook.${inventory_id}.yaml" # the linuxkit configuration file
+		)
+
+		log info "Building Hook ISO with kernel ${inventory_id} using linuxkit: ${lk_iso_args[*]}"
+		"${linuxkit_bin}" build "${lk_iso_args[@]}"
+	fi
+
 	declare initramfs_path="${lk_output_dir}/hook-initrd.img"
 	# initramfs_path is a gzipped file. obtain the uncompressed byte size, without decompressing it
 	declare -i initramfs_size_bytes=0