ui/console-vc: Silence warning about sprintf() on OpenBSD

The linker on OpenBSD complains:

 ld: warning: console-vc.c:824 (../src/ui/console-vc.c:824)([...]):
 warning: sprintf() is often misused, please use snprintf()

Using g_strdup_printf() is certainly better here, so let's switch
to that function instead.

Signed-off-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Michael Tokarev <mjt@tls.msk.ru>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

ui/console-vc.c

@@ -648,7 +648,7 @@ static void vc_putchar(VCChardev *vc, int ch)
     QemuTextConsole *s = vc->console;
     int i;
     int x, y;
-    char response[40];
+    g_autofree char *response = NULL;
 
     switch(vc->state) {
     case TTY_STATE_NORM:
@@ -821,7 +821,7 @@ static void vc_putchar(VCChardev *vc, int ch)
                     break;
                 case 6:
                     /* report cursor position */
-                    sprintf(response, "\033[%d;%dR",
+                    response = g_strdup_printf("\033[%d;%dR",
                            (s->y_base + s->y) % s->total_height + 1,
                             s->x + 1);
                     vc_respond_str(vc, response);