build: new option to build plugins within the daemon binary

Instead of creating libmm-plugin* and libmm-shared* libraries that are
dlopen()-ed on runtime, allow incorporating all plugins into the
daemon binary itself.

This makes the startup of the daemon much faster and also avoids
issues with builds that require linker namespace isolation.

Fixes https://gitlab.freedesktop.org/mobile-broadband/ModemManager/-/issues/674

src/mm-base-manager.c

@@ -68,7 +68,9 @@ enum {
     PROP_CONNECTION,
     PROP_AUTO_SCAN,
     PROP_FILTER_POLICY,
+#if !defined WITH_BUILTIN_PLUGINS
     PROP_PLUGIN_DIR,
+#endif
     PROP_INITIAL_KERNEL_EVENTS,
 #if defined WITH_TESTS
     PROP_ENABLE_TEST,
@@ -83,8 +85,10 @@ struct _MMBaseManagerPrivate {
     gboolean auto_scan;
     /* Filter policy (mask of enabled rules) */
     MMFilterRule filter_policy;
+#if !defined WITH_BUILTIN_PLUGINS
     /* Path to look for plugins */
     gchar *plugin_dir;
+#endif
     /* Path to the list of initial kernel events */
     gchar *initial_kernel_events;
     /* The authorization provider */
@@ -1380,7 +1384,9 @@ log_object_build_id (MMLogObject *_self)
 
 MMBaseManager *
 mm_base_manager_new (GDBusConnection  *connection,
+#if !defined WITH_BUILTIN_PLUGINS
                      const gchar      *plugin_dir,
+#endif
                      gboolean          auto_scan,
                      MMFilterRule      filter_policy,
                      const gchar      *initial_kernel_events,
@@ -1395,7 +1401,9 @@ mm_base_manager_new (GDBusConnection  *connection,
                            NULL, /* cancellable */
                            error,
                            MM_BASE_MANAGER_CONNECTION,            connection,
+#if !defined WITH_BUILTIN_PLUGINS
                            MM_BASE_MANAGER_PLUGIN_DIR,            plugin_dir,
+#endif
                            MM_BASE_MANAGER_AUTO_SCAN,             auto_scan,
                            MM_BASE_MANAGER_FILTER_POLICY,         filter_policy,
                            MM_BASE_MANAGER_INITIAL_KERNEL_EVENTS, initial_kernel_events,
@@ -1445,10 +1453,12 @@ set_property (GObject      *object,
     case PROP_FILTER_POLICY:
         self->priv->filter_policy = g_value_get_flags (value);
         break;
+#if !defined WITH_BUILTIN_PLUGINS
     case PROP_PLUGIN_DIR:
         g_free (self->priv->plugin_dir);
         self->priv->plugin_dir = g_value_dup_string (value);
         break;
+#endif
     case PROP_INITIAL_KERNEL_EVENTS:
         g_free (self->priv->initial_kernel_events);
         self->priv->initial_kernel_events = g_value_dup_string (value);
@@ -1482,9 +1492,11 @@ get_property (GObject    *object,
     case PROP_FILTER_POLICY:
         g_value_set_flags (value, self->priv->filter_policy);
         break;
+#if !defined WITH_BUILTIN_PLUGINS
     case PROP_PLUGIN_DIR:
         g_value_set_string (value, self->priv->plugin_dir);
         break;
+#endif
     case PROP_INITIAL_KERNEL_EVENTS:
         g_value_set_string (value, self->priv->initial_kernel_events);
         break;
@@ -1548,7 +1560,11 @@ initable_init (GInitable     *initable,
         return FALSE;
 
     /* Create plugin manager */
-    self->priv->plugin_manager = mm_plugin_manager_new (self->priv->plugin_dir, self->priv->filter, error);
+    self->priv->plugin_manager = mm_plugin_manager_new (self->priv->filter,
+#if !defined WITH_BUILTIN_PLUGINS
+                                                        self->priv->plugin_dir,
+#endif
+                                                        error);
     if (!self->priv->plugin_manager)
         return FALSE;
 
@@ -1613,7 +1629,9 @@ finalize (GObject *object)
     MMBaseManager *self = MM_BASE_MANAGER (object);
 
     g_free (self->priv->initial_kernel_events);
+#if !defined WITH_BUILTIN_PLUGINS
     g_free (self->priv->plugin_dir);
+#endif
 
     g_hash_table_destroy (self->priv->inhibited_devices);
     g_hash_table_destroy (self->priv->devices);
@@ -1704,6 +1722,7 @@ mm_base_manager_class_init (MMBaseManagerClass *manager_class)
                             MM_FILTER_RULE_NONE,
                             G_PARAM_READWRITE | G_PARAM_CONSTRUCT_ONLY));
 
+#if !defined WITH_BUILTIN_PLUGINS
     g_object_class_install_property
         (object_class, PROP_PLUGIN_DIR,
          g_param_spec_string (MM_BASE_MANAGER_PLUGIN_DIR,
@@ -1711,6 +1730,7 @@ mm_base_manager_class_init (MMBaseManagerClass *manager_class)
                               "Where to look for plugins",
                               NULL,
                               G_PARAM_READWRITE | G_PARAM_CONSTRUCT_ONLY));
+#endif
 
     g_object_class_install_property
         (object_class, PROP_INITIAL_KERNEL_EVENTS,