extensions-app: Include a non-fake Config

We currently include a fake config.js file to satisfy the indirect
import from ExtensionUtils. However we're about to need to pass
build-time information into the program ourselves, so generate
a proper file.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2841>

subprojects/extensions-app/js/meson.build

@@ -26,6 +26,8 @@ configure_file(
   install_dir: pkgdatadir,
 )
 
+subdir('misc')
+
 gnome.compile_resources(
   app_id + '.src',
   configure_file(
@@ -33,7 +35,7 @@ gnome.compile_resources(
     output: app_id + '.src.gresource.xml',
     configuration: {'profile': '/'.join(profile.split('.')) },
   ),
-  source_dir: ['.', '../../../js'],
+  source_dir: ['.', meson.current_build_dir(), '../../../js'],
   gresource_bundle: true,
   install: true,
   install_dir: pkgdatadir

subprojects/extensions-app/js/misc/config.js

@@ -1 +0,0 @@
-/* Fake module to satify import in ExtensionUtils */

subprojects/extensions-app/js/misc/config.js.in

@@ -0,0 +1 @@
+var PACKAGE_VERSION = '@PACKAGE_VERSION@';

subprojects/extensions-app/js/misc/meson.build

@@ -0,0 +1,7 @@
+config_js = configure_file(
+  input: 'config.js.in',
+  output: '@BASENAME@',
+  configuration: {
+    'GETTEXT_VERSION': meson.project_version(),
+  }
+)