darwin.xattr: replace with xattr from file_cmds

file_cmds 352.40.6 added a C-based implementation of xattr, which is the
version of xattr used on recent releases of macOS. Align nixpkgs with
what macOS is shipping, which has also the benefit of allowing xattr to
be cross-compiled (previously precluded due to Python limitations).

pkgs/os-specific/darwin/xattr/default.nix

@@ -1,78 +0,0 @@
-{ lib
-, fetchFromGitHub
-, buildPythonPackage
-, python
-, ed
-, unifdef
-}:
-
-buildPythonPackage rec {
-  pname = "xattr";
-  version = "61.60.1";
-
-  src = fetchFromGitHub {
-    owner = "apple-oss-distributions";
-    repo = "python_modules";
-    rev = "python_modules-${version}";
-    hash = "sha256-kfMGPzNAJsPvvUCSzcR0kgg85U6/NFf/ie1uwg9tfqY=";
-  };
-
-  sourceRoot = "${src.name}/Modules/xattr-0.6.4";
-  format = "other";
-
-  nativeBuildInputs = [
-    ed
-    unifdef
-    python.pkgs.setuptools
-  ];
-
-  makeFlags = [
-    "OBJROOT=$(PWD)"
-    "DSTROOT=${placeholder "out"}"
-    "OSL=${placeholder "doc"}/share/xattr/OpenSourceLicenses"
-    "OSV=${placeholder "doc"}/share/xattr/OpenSourceVersions"
-  ];
-
-  # need to use `out` instead of `bin` since buildPythonPackage ignores the latter
-  outputs = [ "out" "doc" "python" ];
-
-  # We need to patch a reference to gnutar in an included Makefile
-  postUnpack = ''
-    chmod u+w $sourceRoot/..
-  '';
-
-  postPatch = ''
-    substituteInPlace ../Makefile.inc --replace gnutar tar
-    substituteInPlace Makefile --replace "/usr" ""
-  '';
-
-  preInstall = ''
-    # prevent setup.py from trying to download setuptools
-    sed -i xattr-*/setup.py -e '/ez_setup/d'
-
-    # create our custom target dirs we patch in
-    mkdir -p "$doc/share/xattr/"OpenSource{Licenses,Versions}
-    mkdir -p "$python/lib/${python.libPrefix}"
-  '';
-
-  # move python package to its own output to reduce clutter
-  postInstall = ''
-    mv "$out/lib/python" "$python/${python.sitePackages}"
-    rmdir "$out/lib"
-  '';
-
-  makeWrapperArgs = [
-    "--prefix"
-    "PYTHONPATH"
-    ":"
-    "${placeholder "python"}/${python.sitePackages}"
-  ];
-
-  meta = with lib; {
-    description = "Display and manipulate extended attributes";
-    license = [ licenses.psfl licenses.mit ]; # see $doc/share/xattr/OpenSourceLicenses
-    maintainers = [ maintainers.sternenseemann ];
-    homepage = "https://opensource.apple.com/source/python_modules/";
-    platforms = lib.platforms.darwin;
-  };
-}

pkgs/top-level/darwin-packages.nix

@@ -221,7 +221,7 @@ impure-cmds // apple-source-packages // apple-source-headers // stubs // {
 
   trash = callPackage ../os-specific/darwin/trash { };
 
-  xattr = pkgs.python3Packages.callPackage ../os-specific/darwin/xattr { };
+  inherit (self.file_cmds) xattr;
 
   inherit (pkgs.callPackages ../os-specific/darwin/xcode { })
     xcode_8_1 xcode_8_2