build_library: fix a bug when setting a CDROM image

Setting `$VM_CDROM` in the qemu script does not work as expected when
installing Container Linux from the given bootable CDROM image. That's
probably because qemu-system-x86_64 expects another boot option `-boot
order=d` to be able to boot from the given CDROM drive. Let's specify
specify a `-boot` as well as `-drive` option for the given CDROM drive.

build_library/qemu_template.sh

@@ -198,7 +198,8 @@ if [ -n "${VM_UUID}" ]; then
 fi
 
 if [ -n "${VM_CDROM}" ]; then
-    set -- -cdrom "${SCRIPT_DIR}/${VM_CDROM}" "$@"
+    set -- -boot order=d \
+	-drive file="${SCRIPT_DIR}/${VM_CDROM}",media=cdrom,format=raw "$@"
 fi
 
 if [ -n "${VM_PFLASH_RO}" ] && [ -n "${VM_PFLASH_RW}" ]; then