Make sure we build against older ostree (without gpg import)

This means we work on the f22 ostree version at least.

app/xdg-app-builtins-add-remote.c

@@ -120,9 +120,14 @@ import_keys (XdgAppDir *dir,
       if (!open_source_stream (&input_stream, cancellable, error))
         return FALSE;
 
+#ifdef HAVE_OSTREE_REPO_REMOTE_GPG_IMPORT
       if (!ostree_repo_remote_gpg_import (xdg_app_dir_get_repo (dir), remote_name, input_stream,
                                           NULL, &imported, cancellable, error))
         return FALSE;
+#else
+      if (FALSE)
+        return xdg_app_fail (error, "gpg key import not supported by libostree, use --no-gpg-verify");
+#endif
 
       /* XXX If we ever add internationalization, use ngettext() here. */
       g_print ("Imported %u GPG key%s to remote \"%s\"\n",

configure.ac

@@ -59,9 +59,15 @@ AC_SUBST(BASE_LIBS)
 PKG_CHECK_MODULES(SOUP, [libsoup-2.4])
 AC_SUBST(SOUP_CFLAGS)
 AC_SUBST(SOUP_LIBS)
+
 PKG_CHECK_MODULES(OSTREE, [libgsystem >= 2015.1 ostree-1 >= 2015.3])
 AC_SUBST(OSTREE_CFLAGS)
 AC_SUBST(OSTREE_LIBS)
+save_LIBS=$LIBS
+LIBS=$OSTREE_LIBS
+AC_CHECK_FUNCS(ostree_repo_remote_gpg_import)
+LIBS=$save_LIBS
+
 PKG_CHECK_MODULES(FUSE, [fuse])
 AC_SUBST(FUSE_CFLAGS)
 AC_SUBST(FUSE_LIBS)