core-services/03-console-setup.sh: respect localtime hwclock

When TIMEZONE was unset or empty, the resulting empty TZ variable in
the environment caused hwclock to set the timezone to UTC and ignore
the value of /etc/localtime. Only set TZ when TIMEZONE is non-empty.

Thanks to quinq in #voidlinux for finding the root cause of the bug.

hwclock(8):

	The system timezone is configured by the TZ environment variable
	or the /etc/localtime file, as tzset(3) would interpret them.

tzset(3):

	If the TZ variable does appear in the environment, but its value
	is empty, or its value cannot be interpreted using any of the
	formats specified below, then Coordinated Universal Time (UTC)
	is used.

Fixes: 6394a10 (core-services/02-console-setup.sh: setup HARDWARECLOCK if set.)

Author: deepcube

core-services/03-console-setup.sh

@@ -21,6 +21,6 @@ fi
 
 if [ -n "$HARDWARECLOCK" ]; then
     msg "Setting up RTC to '${HARDWARECLOCK}'..."
-    TZ=$TIMEZONE hwclock --systz \
+    eval ${TIMEZONE:+TZ=$TIMEZONE} hwclock --systz \
         ${HARDWARECLOCK:+--$(echo $HARDWARECLOCK |tr A-Z a-z) --noadjfile} || emergency_shell
 fi