Add commented out clock option

This let's you pull the clock into the 21st century if you need a newer
date for SSL certs and haven't done NTP. It's commented out due to
people comparing to 1980 to determine whether NTP has sync'd the time.

Author: fhunleth

rootfs_overlay/etc/erlinit.config

@@ -22,6 +22,11 @@
 #--uid 100
 #--gid 200
 
+# Uncomment to ensure that the system clock is set to at least the Nerves
+# System's build date/time. If you enable this, you'll still need to use NTP or
+# another mechanism to set the clock, but it won't be decades off.
+#--update-clock
+
 # Uncomment to hang the board rather than rebooting when Erlang exits
 # NOTE: Do not enable on production boards
 #--hang-on-exit