[gnome-builder/wip/gtk4-port] plugins/shellcmd: use flat buttons

[Christian Hergert <chergert src gnome org>]

commit 6770c46a08236099748ca69b7cfe697434b969ab
Author: Christian Hergert <chergert redhat com>
Date:   Fri Jun 10 17:42:40 2022 -0700

    plugins/shellcmd: use flat buttons

 src/plugins/shellcmd/gbp-shellcmd-preferences-addin.c | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/src/plugins/shellcmd/gbp-shellcmd-preferences-addin.c 
b/src/plugins/shellcmd/gbp-shellcmd-preferences-addin.c
index 0251bc9b6..9931ca9f1 100644
--- a/src/plugins/shellcmd/gbp-shellcmd-preferences-addin.c
+++ b/src/plugins/shellcmd/gbp-shellcmd-preferences-addin.c
@@ -32,6 +32,7 @@ struct _GbpShellcmdPreferencesAddin
 {
   GObject               parent_instance;
   IdePreferencesWindow *window;
+  GSettings            *settings;
 };
 
 static void
@@ -52,6 +53,7 @@ handle_shellcmd_list (const char                   *page_name,
                                            g_object_new (GTK_TYPE_BUTTON,
                                                          "valign", GTK_ALIGN_CENTER,
                                                          "icon-name", "list-add-symbolic",
+                                                         "css-classes", IDE_STRV_INIT ("flat"),
                                                          NULL));
 
   adw_preferences_group_add (group, gtk_label_new ("empty"));