gi: expose some files as variable for gobject-introspection

see:
https://gitlab.gnome.org/GNOME/gobject-introspection/-/merge_requests/313

glib/meson.build

@@ -1,4 +1,4 @@
-configure_file(input : 'glibconfig.h.in', output : 'glibconfig.h',
+glibconfig_h = configure_file(input : 'glibconfig.h.in', output : 'glibconfig.h',
   install_dir : join_paths(get_option('libdir'), 'glib-2.0/include'),
   configuration : glibconfig_conf)
 
@@ -120,6 +120,10 @@ glib_headers = files(
 )
 install_headers(glib_headers, subdir : 'glib-2.0')
 
+# Expose as variable to be used by gobject-introspection
+# when it includes GLib as a subproject
+glib_unix_h = files('glib-unix.h')
+
 glib_deprecated_headers = files(
   'deprecated/gallocator.h',
   'deprecated/gcache.h',

gmodule/meson.build

@@ -59,9 +59,14 @@ gmoduleconf_h = configure_file(input : 'gmoduleconf.h.in',
                                output : 'gmoduleconf.h',
                                configuration : gmoduleconf_conf)
 
-install_headers(['gmodule.h'], subdir : 'glib-2.0')
+# Expose as variable to be used by gobject-introspection
+# when it includes GLib as a subproject
+gmodule_h = files('gmodule.h')
+gmodule_c = files('gmodule.c')
 
-gmodule_sources = ['gmodule.c']
+install_headers([gmodule_h], subdir : 'glib-2.0')
+
+gmodule_sources = [gmodule_c]
 if host_system == 'windows'
   gmodule_win_rc = configure_file(
     input: 'gmodule.rc.in',

gobject/meson.build

@@ -117,6 +117,10 @@ glib_enumtypes_c = custom_target('glib_enumtypes_c',
 
 glib_enumtypes_dep = declare_dependency(sources : [glib_enumtypes_h])
 
+# Expose as variable to be used by gobject-introspection
+# when it includes GLib as a subproject
+glib_types_h = files('glib-types.h')
+
 libgobject = library('gobject-2.0',
   gobject_dtrace_obj, gobject_dtrace_hdr, glib_enumtypes_h, glib_enumtypes_c,
   sources : gobject_sources,