Shutdown the container on abnormal signals (home-assistant#55660)

So far the finish script exits whenever the service terminated by a
signal (indicated by 256 as first argument). This is the intended
behavior when SIGTERM is being sent: SIGTERM is used on regular shutdown
through the supervisor. We don't want the finish script to shutdown
itself while being taken down by the supervisor already.

However, every other signal which lead to a process exit likely means
trouble: SIGSEGV, SIGILL, etc. In those cases we want the container to
exit. The Supervisor (or restart policy of Docker in the container case)
will take care of restarting if appropriate.

rootfs/etc/services.d/home-assistant/finish

@@ -2,7 +2,19 @@
 # ==============================================================================
 # Take down the S6 supervision tree when Home Assistant fails
 # ==============================================================================
-if { s6-test ${1} -ne 100 }
-if { s6-test ${1} -ne 256 }
+define HA_RESTART_EXIT_CODE 100
+define SIGNAL_EXIT_CODE 256
+define SIGTERM 15
+
+foreground { s6-echo "[finish] process exit code ${1}" }
+
+if { s6-test ${1} -ne ${HA_RESTART_EXIT_CODE} }
+ifelse { s6-test ${1} -eq ${SIGNAL_EXIT_CODE} } {
+  # Process terminated by a signal
+  define signal ${2}
+  foreground { s6-echo "[finish] process received signal ${signal}" }
+  if { s6-test ${signal} -ne ${SIGTERM} }
+  s6-svscanctl -t /var/run/s6/services
+}
 
 s6-svscanctl -t /var/run/s6/services