[gnome-shell] hotplug-sniffer: Add gnu_printf format attribute

[Florian Müllner <fmuellner src gnome org>]

commit 1dff32e48a6727833344e1f1fd2237385483ba77
Author: Robert Mader <robert mader posteo de>
Date:   Tue Mar 5 23:43:01 2019 +0100

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

 src/hotplug-sniffer/hotplug-sniffer.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/src/hotplug-sniffer/hotplug-sniffer.c b/src/hotplug-sniffer/hotplug-sniffer.c
index c229af51f..31e45795e 100644
--- a/src/hotplug-sniffer/hotplug-sniffer.c
+++ b/src/hotplug-sniffer/hotplug-sniffer.c
@@ -266,7 +266,7 @@ main (int    argc,
 
 /* ---------------------------------------------------------------------------------------------------- */
 
-static void
+static void __attribute__((format(printf, 1, 0)))
 print_debug (const gchar *format, ...)
 {
   gchar *s;