add VNC support to run_archiso.sh

Usage: Launch run_archiso.sh -v ..., and then use a VNC viewer
(e.g. from https://wiki.archlinux.org/index.php/List_of_applications/Internet#Remote_desktop)
to connect (typically to `localhost`) on the default VNC port (5900).

This enables using run_archiso in a "headless" session; e.g. when SSH logged in
to the CLI of a VM, without a local display attached.  This is handy e.g. when
playing https://en.wikipedia.org/wiki/Inception and running an archlinux*.iso
on any non-Arch (say Fedora workstation), on which one built a new ISO, that you
then "run_archiso", inside which you could build another ISO, which you could
itself start inside the nested VM... ;-)

Jokes apart, this could also be used to run automated CI/CD tests of the built ISO,
which is particularly interesting in combination with the cloud-init support;
see https://wiki.archlinux.org/index.php/Cloud-init.

see https://bugs.archlinux.org/task/69142

scripts/run_archiso.sh

@@ -28,6 +28,7 @@ Options:
     -i [image]      image to boot into
     -s              use Secure Boot (only relevant when using UEFI)
     -u              set boot type to 'UEFI'
+    -v              use VNC display (instead of default SDL)
 
 Example:
     Run an image using UEFI:
@@ -87,12 +88,12 @@ run_image() {
     qemu-system-x86_64 \
         -boot order=d,menu=on,reboot-timeout=5000 \
         -m "size=3072,slots=0,maxmem=$((3072*1024*1024))" \
-        -k en \
+        -k en-us \
         -name archiso,process=archiso_0 \
         -device virtio-scsi-pci,id=scsi0 \
         -device "scsi-${mediatype%rom},bus=scsi0.0,drive=${mediatype}0" \
         -drive "id=${mediatype}0,if=none,format=raw,media=${mediatype/hd/disk},readonly=on,file=${image}" \
-        -display sdl \
+        -display "${display}" \
         -vga virtio \
         -audiodev pa,id=snd0 \
         -device ich9-intel-hda \
@@ -123,12 +124,13 @@ accessibility=''
 boot_type='bios'
 mediatype='cdrom'
 secure_boot='off'
+display='sdl'
 qemu_options=()
 working_dir="$(mktemp -dt run_archiso.XXXXXXXXXX)"
 trap cleanup_working_dir EXIT
 
 if (( ${#@} > 0 )); then
-    while getopts 'abdhi:su' flag; do
+    while getopts 'abdhi:suv' flag; do
         case "$flag" in
             a)
                 accessibility='on'
@@ -152,6 +154,10 @@ if (( ${#@} > 0 )); then
             s)
                 secure_boot='on'
                 ;;
+            v)
+                display='none'
+                qemu_options+=(-vnc 'vnc=0.0.0.0:0,vnc=[::]:0')
+                ;;
             *)
                 printf '%s\n' "Error: Wrong option. Try 'run_archiso -h'."
                 exit 1