dbusServices/screencast: Install unconditionally

We currently decide at build time whether to include screencast
support, based on whether the required gst/pipewire library headers
are installed.

That check is imprecise, because having the library headers available
at build time doesn't necessarily mean that the libraries are there
at runtime, or that the corresponding typelibs are installed.

It makes more sense to check the requirements at runtime, so prepare
for that by installing the screencast service unconditionally, but
bail out early if the dependencies aren't met.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2297>

js/dbusServices/meson.build

@@ -6,15 +6,10 @@ launcherconf.set('libdir', libdir)
 dbus_services = {
   'org.gnome.Shell.Extensions': 'extensions',
   'org.gnome.Shell.Notifications': 'notifications',
+  'org.gnome.Shell.Screencast': 'screencast',
   'org.gnome.ScreenSaver': 'screensaver',
 }
 
-if enable_recorder
-  dbus_services += {
-    'org.gnome.Shell.Screencast': 'screencast',
-  }
-endif
-
 config_dir = '@0@/..'.format(meson.current_build_dir())
 
 foreach service, dir : dbus_services

js/dbusServices/screencast/main.js

@@ -1,9 +1,13 @@
 /* exported main */
 
+const Config = imports.misc.config;
 const { DBusService } = imports.dbusService;
-const { ScreencastService } = imports.screencastService;
 
 function main() {
+    if (!Config.HAVE_RECORDER)
+        return;
+
+    const { ScreencastService } = imports.screencastService;
     const service = new DBusService(
         'org.gnome.Shell.Screencast',
         new ScreencastService());