freeault: Add `meta.pkgConfigModules` and test

pkgs/development/libraries/freealut/default.nix

···
-{ lib, stdenv, darwin, fetchurl, openal }:
+{ lib, stdenv, darwin, fetchurl, openal
+, testers
+}:
 
-stdenv.mkDerivation rec {
+stdenv.mkDerivation (finalAttrs: {
   pname = "freealut";
   version = "1.1.0";
 
   src = fetchurl {
-    url = "http://www.openal.org/openal_webstf/downloads/freealut-${version}.tar.gz";
+    url = "http://www.openal.org/openal_webstf/downloads/freealut-${finalAttrs.version}.tar.gz";
     sha256 = "0kzlil6112x2429nw6mycmif8y6bxr2cwjcvp18vh6s7g63ymlb0";
   };
 
···
   ] ++ lib.optional stdenv.isDarwin
     darwin.apple_sdk.frameworks.OpenAL
   ;
+
+  passthru.tests.pkg-config = testers.testMetaPkgConfig finalAttrs.finalPackage;
 
   meta = {
     homepage = "http://openal.org/";
     description = "Free implementation of OpenAL's ALUT standard";
     license = lib.licenses.lgpl2;
+    pkgConfigModules = [ "freealut" ];
     platforms = lib.platforms.unix;
   };
-}
+})