anchor.diff:    withToolset = stdenv.lib.optionalString (toolset != null) "--with-toolset=${toolset}";
   
     genericB2Flags = [
  -    "--prefix=$dev"
  +    "--includedir=$dev/include"
       "--libdir=$lib/lib"
       "-j$NIX_BUILD_CORES"
       "--layout=${layout}"
  
positive.code: 
      # Create a derivation which encompasses everything, making buildInputs nicer
      mkdir -p $out/nix-support
      echo $dev >> $out/nix-support/propagated-build-inputs
      echo $lib >> $out/nix-support/propagated-build-inputs
    '';
  
    commonConfigureFlags = [
      "--libdir=$(lib)/lib"
    ];
  in
  
negative.code:     # We want to substitute the contents of configureFlags, removing thus the
      # usual --build and --host added on cross building.
      preConfigure = ''
        export configureFlags="--without-icu ${concatStringsSep " " commonConfigureFlags}"
        set -x
        cat << EOF > user-config.jam
        using gcc : cross : $crossConfig-g++ ;
  