meson: Automatically link libglnx-dependent objects to gio-unix

If we don't do this, users of libglnx all have to add this dependency
themselves, otherwise they'll get errors like:

    fatal error: gio/gfiledescriptorbased.h: No such file or directory

Signed-off-by: Simon McVittie <smcv@collabora.com>

meson.build

@@ -86,6 +86,7 @@ libglnx = static_library('glnx',
   include_directories : libglnx_inc,
   install : false)
 libglnx_dep = declare_dependency(
+  dependencies : libglnx_deps,
   include_directories : libglnx_inc,
   link_with : libglnx)