anchor.diff: -{ lib, stdenv, fetchurl, bison }:
  +{ lib, stdenv, fetchurl, bison, buildPackages }:
   
   let
     mkJam = { meta ? { }, ... } @ args: stdenv.mkDerivation (args // {
  +    depsBuildBuild = [ buildPackages.stdenv.cc ];
       nativeBuildInputs = [ bison ];
   
       # Jambase expects ar to have flags.
  
positive.code:   in mkJam {
      inherit pname version;
  
      postPatch = ''
        substituteInPlace Jamfile --replace strip ${stdenv.cc.targetPrefix}strip
      '';
  
      src = fetchurl {
        url = "https://downloads.sourceforge.net/project/freetype/${pname}/${version}/${pname}-${version}.tar.bz2";
        hash = "sha256-6JdzUAqSkS3pGOn+v/q+S2vOedaa8ZRDX04DK4ptZqM=";
      };
  
      meta = with lib; {
        description = "FreeType's enhanced, backwards-compatible Jam clone";
  
negative.code:       export AR="$AR rc"
      '';
  
      LOCATE_TARGET = "bin.unix";
  
      buildPhase = ''
        runHook preBuild
        make $makeFlags jam0
        ./jam0 -j$NIX_BUILD_CORES -sCC=${buildPackages.stdenv.cc.targetPrefix}cc jambase.c
        ./jam0 -j$NIX_BUILD_CORES
        runHook postBuild
      '';
  
      installPhase = ''
        runHook preInstall
        mkdir -p $out/bin $out/doc/jam
        cp bin.unix/jam $out/bin/jam
        cp *.html $out/doc/jam
        runHook postInstall
      '';
  
  