[gnome-flashback] monitor-config-manager: mark the mirroring logical monitor as primary

[Alberts Muktupāvels <muktupavels src gnome org>]

commit 1732ca8b7d4a8adebe77bdb761bd5fb69ed43b89
Author: Alberts Muktupāvels <alberts muktupavels gmail com>
Date:   Fri Aug 19 20:29:22 2022 +0300

    monitor-config-manager: mark the mirroring logical monitor as primary
    
    Based on mutter commit:
    https://gitlab.gnome.org/GNOME/mutter/-/commit/8698b4a493d00b79115ad655373803e5238e529c

 backends/gf-monitor-config-manager.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
---
diff --git a/backends/gf-monitor-config-manager.c b/backends/gf-monitor-config-manager.c
index 54dfadc..11e8070 100644
--- a/backends/gf-monitor-config-manager.c
+++ b/backends/gf-monitor-config-manager.c
@@ -455,7 +455,8 @@ create_for_switch_config_all_mirror (GfMonitorConfigManager *config_manager)
       .height = height
     },
     .scale = best_scale,
-    .monitor_configs = monitor_configs
+    .monitor_configs = monitor_configs,
+    .is_primary = TRUE
   };
 
   logical_monitor_configs = g_list_append (NULL, logical_monitor_config);