live: add use/live/runapp

Add the possibility to directly configure the desktop app
for livecd kiosk mode to start.

This should have been done as soon as livecd-runapp
hit the streets -- livecd-{0ad,fgfs} definitely must go
as adding a line into config is trivially done near
the only place that requires them (conf.d/live.mk).

TODO: might be more generally useful for vm/* too,
      take this out into a separate feature then.

Edited: https://lists.altlinux.org/pipermail/devel-distro/2022-September/002889.html

features.in/live/README

@@ -19,3 +19,8 @@
 ** перечисляет префиксы каталогов драйвров ядра для удаления
 ** значение: пусто (по умолчанию) или список через пробел
 ** см. config.mk
+
+* LIVE_RUNAPP_BINARY
+** указывает имя программы для запуска в режиме киоска
+** значение: пусто (по умолчанию) или путь (из $PATH или полный)
+** см. тж. пакеты livecd-0ad, livecd-fgfs и сам livecd-runapp

features.in/live/config.mk

@@ -99,6 +99,11 @@ else
 use/live/suspend: use/live; @:
 endif
 
+# for kiosks
+use/live/runapp: use/live;
+	@$(call add,LIVE_PACKAGES,livecd-runapp)
+	@$(call xport,LIVE_RUNAPP_BINARY)
+
 # deny network/local drive access for security reasons
 use/live/privacy: use/services use/memclean use/deflogin \
 	use/stage2/ata use/stage2/drm use/stage2/hid \

features.in/live/live/image-scripts.d/50-runapp

@@ -0,0 +1,19 @@
+#!/bin/sh -efux
+# see also live-0ad
+
+rpm -q livecd-runapp || exit 0
+[ -n "${GLOBAL_LIVE_RUNAPP_BINARY:-}" ] || exit 0
+
+CONFIG=/etc/sysconfig/livecd-runapp
+
+if [ -s "$CONFIG" ]; then
+	echo "$CONFIG exists, not overriding (from $(rpm -qf "$CONFIG"))"
+	exit 0
+fi
+
+mkdir -p "$(dirname "$CONFIG")"
+cat >> "$CONFIG" << _EOF_
+# mkimage-profiles live 50-runapp hook
+BINARY=$GLOBAL_LIVE_RUNAPP_BINARY
+_EOF_
+: