libvorbis: use pkgconfig instead of guessing paths. Closes #3014

pkgs/development/libraries/libvorbis/default.nix

@@ -1,4 +1,4 @@
-{ stdenv, fetchurl, libogg }:
+{ stdenv, fetchurl, libogg, pkgconfig }:
 
 let
   name = "libvorbis-1.3.4";
@@ -11,6 +11,8 @@ stdenv.mkDerivation {
     sha256 = "0wpk87jnhngcl3nc5i39flkycx1sjzilx8jjx4zc4p8r55ylj19g";
   };
 
+  buildInputs = [ pkgconfig ];
+
   propagatedBuildInputs = [ libogg ];
 
   doCheck = true;