gst-launch: ship default plugins

hosts/common/programs/gst-launch.nix

@@ -1,6 +1,23 @@
+# basic environment tests:
+# - `gst-launch-1.0 audiotestsrc ! autoaudiosink`
+# - `gst-launch-1.0 videotestsrc ! videoconvert ! autovideosink`
+# more usage here: <https://github.com/matthew1000/gstreamer-cheat-sheet>
 { pkgs, ... }:
 {
   sane.programs.gst-launch = {
-    packageUnwrapped = pkgs.linkBinIntoOwnPackage pkgs.gst_all_1.gstreamer "gst-launch-1.0";
+    packageUnwrapped = (
+      pkgs.linkBinIntoOwnPackage pkgs.gst_all_1.gstreamer "gst-launch-1.0"
+    ).overrideAttrs (base: {
+      # XXX the binaries need `GST_PLUGIN_SYSTEM_PATH_1_0` set to function,
+      # but nixpkgs doesn't set those.
+      nativeBuildInputs = (base.nativeBuildInputs or []) ++ [
+        pkgs.wrapGAppsNoGuiHook
+      ];
+      buildInputs = (base.buildInputs or []) ++ [
+        pkgs.gst_all_1.gst-plugins-base
+        pkgs.gst_all_1.gst-plugins-good
+        pkgs.pipewire
+      ];
+    });
   };
 }