ArchLinux: give correct UUID for img_dev parameter

boot/isos.cfg.d/archlinux.cfg

@@ -12,6 +12,14 @@ for isofile in ${this_isopath}/archlinux*.iso ${this_isopath}/ipxe*; do
 submenu "ArchLinux >" "${this_isopath}" --class arch {
 this_isopath=$2
 
+# find the uuid for this isopath
+regexp \
+    --set 1:isodev \
+    "^(\(.*\)).*\$" "${this_isopath}"
+
+probe -u ${isodev} --set this_uuid
+
+
 menuentry "ArchLinux BIOS netboot" --class arch {
 	echo "Booting ArchLinux BIOS netboot"
 	linux16 ${this_isopath}/ipxe.419cd003a298.lkrn
@@ -46,7 +54,7 @@ for isofile in ${this_isopath}/archlinux-*.iso; do
 
 		echo "Using ${isoname}..."
 		loopback loop "${isodev}${isofile}"
-		linux (loop)/arch/boot/x86_64/vmlinuz-linux img_dev=/dev/disk/by-uuid/${rootuuid} img_loop=${isofile}
+		linux (loop)/arch/boot/x86_64/vmlinuz-linux img_dev=/dev/disk/by-uuid/${this_uuid} img_loop=${isofile}
 		initrd (loop)/arch/boot/intel-ucode.img (loop)/arch/boot/amd-ucode.img (loop)/arch/boot/x86_64/initramfs-linux.img
 	}
 done