haskell-hslua: remove support for linking the system's lua library

This feature is broken: <https://github.com/osa1/hslua/issues/8>.

pkgs/development/libraries/haskell/hslua/default.nix

@@ -1,12 +1,10 @@
-{ cabal, lua, mtl }:
+{ cabal, mtl }:
 
 cabal.mkDerivation (self: {
   pname = "hslua";
   version = "0.3.7";
   sha256 = "1q5s2b7x9idvdvp31yl86mmy476gfq6rg8f0r8faqxrm45jwgv2q";
   buildDepends = [ mtl ];
-  pkgconfigDepends = [ lua ];
-  configureFlags = "-fsystem-lua";
   meta = {
     description = "A Lua language interpreter embedding in Haskell";
     license = self.stdenv.lib.licenses.bsd3;