[gnome-shell] calendar-server: Add gnu_printf format attribute

[Florian Müllner <fmuellner src gnome org>]

commit 2b1d6e607f957ea07314df244169f895410fd21f
Author: Robert Mader <robert mader posteo de>
Date:   Tue Mar 5 23:45:44 2019 +0100

    calendar-server: Add gnu_printf format attribute
    
    Suggested by compiler with `-Wsuggest-attribute=format`
    
    https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/441

 src/calendar-server/gnome-shell-calendar-server.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/src/calendar-server/gnome-shell-calendar-server.c 
b/src/calendar-server/gnome-shell-calendar-server.c
index 9b76fb073..2ad8fb99e 100644
--- a/src/calendar-server/gnome-shell-calendar-server.c
+++ b/src/calendar-server/gnome-shell-calendar-server.c
@@ -1078,7 +1078,7 @@ main (int    argc,
 
 /* ---------------------------------------------------------------------------------------------------- */
 
-static void
+static void __attribute__((format(printf, 1, 0)))
 print_debug (const gchar *format, ...)
 {
   gchar *s;