rtla/utils: Fix session duration parsing

Use gmtime to format the duration time. This avoids problems when the
system uses local time different of Pisa's Local Time.

Link: https://lkml.kernel.org/r/a2f0a37bc006c2561bb8ecd871cd70532b4a9f2d.1643990447.git.bristot@kernel.org

Fixes: b1696371 ("rtla: Helper functions for rtla")
Cc: Daniel Bristot de Oliveira <bristot@kernel.org>
Cc: linux-kernel@vger.kernel.org
Cc: linux-trace-devel@vger.kernel.org
Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

tools/tracing/rtla/src/utils.c

@@ -77,11 +77,11 @@ void get_duration(time_t start_time, char *output, int output_size)
 	time_t duration;
 
 	duration = difftime(now, start_time);
-	tm_info = localtime(&duration);
+	tm_info = gmtime(&duration);
 
 	snprintf(output, output_size, "%3d %02d:%02d:%02d",
 			tm_info->tm_yday,
-			tm_info->tm_hour - 1,
+			tm_info->tm_hour,
 			tm_info->tm_min,
 			tm_info->tm_sec);
 }