Add a note about hwclock and timesyncd.

git-svn-id: http://svn.linuxfromscratch.org/LFS/branches/systemd/BOOK@10724 4aa44e1e-78dd-0310-a6d2-fbcd4c07a689

chapter07/clock.xml

@@ -95,6 +95,10 @@ EOF</userinput></screen>
     can be used to change the NTP servers that
     <command>systemd-timesyncd</command> synchronizes with.</para>
 
+    <para>Please note that when system clock is set to Local Time,
+    <command>systemd-timesyncd</command> won't update hardware
+    clock.</para>
+
   </sect2>
 
 </sect1>