anchor.diff:  
     nativeBuildInputs = [ pkgconfig ];
     buildInputs = [ file curl python openssl cmake zlib makeWrapper libgit2 ]
  -    # FIXME: Use impure version of CoreFoundation because of missing symbols.
  -    # CFURLSetResourcePropertyForKey is defined in the headers but there's no
  -    # corresponding implementation in the sources from opensource.apple.com.
  -    ++ stdenv.lib.optionals stdenv.isDarwin [ darwin.apple_sdk.frameworks.CoreFoundation libiconv ];
  +    ++ stdenv.lib.optionals stdenv.isDarwin [ CoreFoundation libiconv ];
   
     LIBGIT2_SYS_USE_PKG_CONFIG=1;
  +
  +  # FIXME: Use impure version of CoreFoundation because of missing symbols.
  +  # CFURLSetResourcePropertyForKey is defined in the headers but there's no
  +  # corresponding implementation in the sources from opensource.apple.com.
  +  preConfigure = stdenv.lib.optionalString stdenv.isDarwin ''
  +    export NIX_CFLAGS_COMPILE="-F${CoreFoundation}/Library/Frameworks $NIX_CFLAGS_COMPILE"
  +  '';
   
     postInstall = ''
       # NOTE: We override the `http.cainfo` option usually specified in
  
positive.code: { stdenv, fetchFromGitHub, file, curl, pkgconfig, python, openssl, cmake, zlib
  , makeWrapper, libiconv, cacert, rustPlatform, rustc, libgit2, darwin
  , version, srcSha, cargoSha256
  , patches ? []}:
  
  rustPlatform.buildRustPackage rec {
    name = "cargo-${version}";
  
negative.code:     wrapProgram "$out/bin/cargo" \
        --suffix PATH : "${rustc}/bin" \
        --set CARGO_HTTP_CAINFO "${cacert}/etc/ssl/certs/ca-bundle.crt" \
        --set SSL_CERT_FILE "${cacert}/etc/ssl/certs/ca-bundle.crt"
    '';
  
    checkPhase = ''
  