[seahorse] build: add required gio-unix-2.0.

[Niels De Graef <nielsdg src gnome org>]

commit de1f8c238c6969cb9ff9316e1fc5f60073285354
Author: Niels De Graef <nielsdegraef gmail com>
Date:   Thu Aug 2 20:01:34 2018 +0200

    build: add required gio-unix-2.0.
    
    Fixes #8.

 meson.build | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/meson.build b/meson.build
index 2c99c2e4..ab722268 100644
--- a/meson.build
+++ b/meson.build
@@ -40,6 +40,7 @@ glib_deps = [
   dependency('glib-2.0',    version: '>=' + min_glib_version),
   dependency('gobject-2.0', version: '>=' + min_glib_version),
   dependency('gio-2.0',     version: '>=' + min_glib_version),
+  dependency('gio-unix-2.0',version: '>=' + min_glib_version),
   dependency('gmodule-2.0', version: '>=' + min_glib_version),
 ]
 gtk = dependency('gtk+-3.0', version: '>= 3.22.0')