log: add warning to help text to inform the inaccuracy of -T option

The timestamps of the "log -T" option are inaccurate because they are
from local_clock(), which returns the raw counter in the local CPU and
it's different from the elapsed wall time.

The dmesg command, which the "log -T" option imitates, has a similar
behavior in nature and a warning in its help text.  Let's add a warning
also to the crash's help text to inform the inaccuracy for now.

Link: https://listman.redhat.com/archives/crash-utility/2021-September/msg00044.html
Reported-by: Martin Moore <[email protected]>
Signed-off-by: Kazuhito Hagio <[email protected]>

Author: k-hagio

help.c

@@ -3893,6 +3893,8 @@ char *help_log[] = {
 "  record format, where the timestamp is contained in each log entry's header.",
 "  ",
 "    -T  Display the message text with human readable timestamp.",
+"        (Be aware that the timestamp could be inaccurate!  The timestamp is",
+"         from local_clock(), which is different from the elapsed wall time.)",
 "    -t  Display the message text without the timestamp; only applicable to the",
 "        variable-length record format.",
 "    -d  Display the dictionary of key/value pair properties that are optionally",