anchor.diff:      # We want to substitute the contents of configureFlags, removing thus the
       # usual --build and --host added on cross building.
       preConfigure = ''
  -      export configureFlags="--prefix=$out --without-icu ${concatStringsSep " " commonConfigureFlags}"
  +      export configureFlags="--prefix=$dev --without-icu ${concatStringsSep " " commonConfigureFlags}"
         set -x
         cat << EOF > user-config.jam
         using gcc : cross : $crossConfig-g++ ;
  
positive.code: 
    installer = b2Args: ''
      # boostbook is needed by some applications
      mkdir -p $out/share/boostbook
      cp -a tools/boostbook/{xsl,dtd} $out/share/boostbook/
  
      # Let boost install everything else
      ./b2 ${b2Args} install
    '';
  
    commonConfigureFlags = [
  
negative.code:   withToolset = stdenv.lib.optionalString (toolset != null) "--with-toolset=${toolset}";
  
    genericB2Flags = [
      "--prefix=$dev"
      "--libdir=$lib/lib"
      "-j$NIX_BUILD_CORES"
      "--layout=${layout}"
  