$NetBSD$

Remove linux-only systemd dependency

--- libgdm/meson.build.orig	2020-12-15 18:16:43.000000000 +0000
+++ libgdm/meson.build
@@ -56,7 +56,6 @@ libgdm_deps = [
   glib_dep,
   gio_dep,
   gio_unix_dep,
-  libsystemd_dep,
   libgdmcommon_dep,
 ]