docs: steam-machine-iso: one build at a time; vminstallsim.sh passes --defaults options

scripts/vminstallsim.sh

@@ -3,12 +3,14 @@
 # who never logged in (no session bus, user systemd or plasmashell) gets
 # `steamify.sh --defaults` from /mnt, visibly in a Konsole on the VM's
 # desktop. Prints the per-component result lines.
-#   scripts/vminstallsim.sh [--fresh]   --fresh: delete and recreate the user first
+#   scripts/vminstallsim.sh [--fresh] [--defaults options...]
+#       --fresh: delete and recreate the user first; the rest goes to
+#       --defaults (e.g. --skip cec,theme --boot desktop)
 # Env: VM_USER / VM_PORT / VM_HOST, SIM_USER (isotest), GUEST_UID (1000).
 set -euo pipefail
 . "$(dirname "$0")/common.sh"
-fresh=""; [[ "${1:-}" == --fresh ]] && fresh=1
-{ printf 'u=%q fresh=%q uid=%q\n' "${SIM_USER:-isotest}" "$fresh" "${GUEST_UID:-1000}"; cat << 'REMOTE'
+fresh=""; [[ "${1:-}" == --fresh ]] && { fresh=1; shift; }
+{ printf 'u=%q fresh=%q uid=%q opts=%q\n' "${SIM_USER:-isotest}" "$fresh" "${GUEST_UID:-1000}" "$*"; cat << 'REMOTE'
 mountpoint -q /mnt || sudo mount -t 9p -o trans=virtio,version=9p2000.L repo /mnt
 [ -n "$fresh" ] && sudo userdel -r "$u" 2>/dev/null
 cat > /tmp/install-sim.sh << SIM
@@ -16,7 +18,7 @@ cat > /tmp/install-sim.sh << SIM
 id $u >/dev/null 2>&1 || { sudo useradd -m -G wheel -s /bin/bash $u; echo "$u:$u" | sudo chpasswd; }
 echo "$u ALL=(ALL) NOPASSWD: ALL" | sudo tee /etc/sudoers.d/10-steamify-install-sim >/dev/null
 sudo -u $u env -i HOME=/home/$u USER=$u LOGNAME=$u PATH=/usr/local/bin:/usr/bin TERM=xterm \
-    bash -c 'cd ~ && /mnt/steamify.sh --defaults < /dev/null' 2>&1 | tee /tmp/install-sim.log
+    bash -c 'cd ~ && /mnt/steamify.sh --defaults $opts < /dev/null' 2>&1 | tee /tmp/install-sim.log
 echo "exit: \${PIPESTATUS[0]}" | tee -a /tmp/install-sim.log
 sudo rm -f /etc/sudoers.d/10-steamify-install-sim
 touch /tmp/install-sim.done