sfwbar: fix SVG icon rendering via wrapGAppsHook3

Add `wrapGAppsHook3` to `nativeBuildInputs` to ensure `sfwbar` can
successfully locate the `gdk-pixbuf` loaders required to render SVG symbolic
icons in default GTK widgets (such as the battery, bluez, and volume
modules).

The inclusion of this hook automatically generates a unified `loaders.cache`
and wraps the resulting binary with the correct `GDK_PIXBUF_MODULE_FILE`
environment variable. Furthermore, it automatically handles the population
of `XDG_DATA_DIRS`, rendering the previous manual `wrapProgram` execution in
`postFixup` redundant.

pkgs/by-name/sf/sfwbar/package.nix

@@ -16,6 +16,7 @@
   makeWrapper,
   docutils,
   wayland-scanner,
+  wrapGAppsHook3,
 }:
 
 stdenv.mkDerivation (finalAttrs: {
@@ -47,13 +48,9 @@ stdenv.mkDerivation (finalAttrs: {
     pkg-config
     makeWrapper
     wayland-scanner
+    wrapGAppsHook3
   ];
 
-  postFixup = ''
-    wrapProgram $out/bin/sfwbar \
-      --suffix XDG_DATA_DIRS : $out/share
-  '';
-
   meta = {
     homepage = "https://github.com/LBCrion/sfwbar";
     description = "Flexible taskbar application for wayland compositors, designed with a stacking layout in mind";