Export flatpak_run_gc_ids()

Currently, we only remove stale instance directories
when a new instance ID is allocated. A future 'flatpak ps'
command will want to remove stale instances before
enumerating them, so make this function available.

Closes: #2023
Approved by: alexlarsson

common/flatpak-run-private.h

@@ -173,5 +173,6 @@ gboolean flatpak_run_app (const char     *app_ref,
                           GCancellable   *cancellable,
                           GError        **error);
 
+void flatpak_run_gc_ids (void);
 
 #endif /* __FLATPAK_RUN_H__ */

common/flatpak-run.c

@@ -1571,7 +1571,7 @@ flatpak_app_compute_permissions (GKeyFile *app_metadata,
   return g_steal_pointer (&app_context);
 }
 
-static void
+void
 flatpak_run_gc_ids (void)
 {
   g_autofree char *base_dir = g_build_filename (g_get_user_runtime_dir (), ".flatpak", NULL);