gdk-pixbuf: Add `meta.pkgConfigModules` and test

pkgs/development/libraries/gdk-pixbuf/default.nix

···
 , doCheck ? false
 , makeWrapper
 , lib
+, testers
 }:
 
-stdenv.mkDerivation rec {
+stdenv.mkDerivation (finalAttrs: {
   pname = "gdk-pixbuf";
   version = "2.42.10";
 
   outputs = [ "out" "dev" "man" "devdoc" ]
     ++ lib.optional (stdenv.buildPlatform == stdenv.hostPlatform) "installedTests";
 
-  src = fetchurl {
+  src = let
+    inherit (finalAttrs) pname version;
+  in fetchurl {
     url = "mirror://gnome/sources/${pname}/${lib.versions.majorMinor version}/${pname}-${version}.tar.xz";
     sha256 = "7ptsddE7oJaQei48aye2G80X9cfr6rWltDnS8uOf5Es=";
   };
···
     '' + lib.optionalString stdenv.isDarwin ''
       # meson erroneously installs loaders with .dylib extension on Darwin.
       # Their @rpath has to be replaced before gdk-pixbuf-query-loaders looks at them.
-      for f in $out/${passthru.moduleDir}/*.dylib; do
+      for f in $out/${finalAttrs.passthru.moduleDir}/*.dylib; do
           install_name_tool -change @rpath/libgdk_pixbuf-2.0.0.dylib $out/lib/libgdk_pixbuf-2.0.0.dylib $f
           mv $f ''${f%.dylib}.so
       done
···
 
   passthru = {
     updateScript = gnome.updateScript {
-      packageName = pname;
+      packageName = finalAttrs.pname;
       versionPolicy = "odd-unstable";
     };
 
     tests = {
       installedTests = nixosTests.installed-tests.gdk-pixbuf;
+      pkg-config = testers.testMetaPkgConfig finalAttrs.finalPackage;
     };
 
     # gdk_pixbuf_moduledir variable from gdk-pixbuf-2.0.pc
···
     license = licenses.lgpl21Plus;
     maintainers = [ maintainers.eelco ] ++ teams.gnome.members;
     mainProgram = "gdk-pixbuf-thumbnailer";
+    pkgConfigModules = [ "gdk-pixbuf-2.0" ];
     platforms = platforms.unix;
   };
-}
+})