[XAM] XamShowSigninUI: Send signin and UI close notification with delay from separate thread

This is to prevent situation when game waits for notification, but receives it beforehand

src/xenia/kernel/xam/xam_user.cc

@@ -548,6 +548,8 @@ dword_result_t XamShowSigninUI_entry(dword_t users_needed, dword_t unk_mask) {
   kernel_state()->UpdateUsedUserProfiles();
   // Mask values vary. Probably matching user types? Local/remote?
   // Games seem to sit and loop until we trigger this notification:
+
+  auto run = [users_needed]() -> void {
     uint32_t user_mask = 0;
     uint32_t active_users = 0;
 
@@ -559,12 +561,17 @@ dword_result_t XamShowSigninUI_entry(dword_t users_needed, dword_t unk_mask) {
       }
     }
 
+    std::this_thread::sleep_for(std::chrono::milliseconds(150));
     // XN_SYS_SIGNINCHANGED (players)
     kernel_state()->BroadcastNotification(kXNotificationIDSystemSignInChanged,
                                           user_mask);
-
     // XN_SYS_UI (off)
     kernel_state()->BroadcastNotification(kXNotificationIDSystemUI, 0);
+  };
+
+  std::thread thread(run);
+  thread.detach();
+
   return X_ERROR_SUCCESS;
 }
 DECLARE_XAM_EXPORT1(XamShowSigninUI, kUserProfiles, kStub);