anchor.diff:  { stdenv, lib, buildPackages, makeWrapper, writeText, runCommand
  -, bash
   , CoreServices, ImageIO, CoreGraphics
   , targetPlatform
   , xcodePlatform ? targetPlatform.xcodePlatform or "MacOSX"
  
positive.code:   '';
  
    xcrun = writeText "xcrun" ''
  #!${bash}/bin/sh
  while [ $# -gt 0 ]; do
     case "$1" in
           --sdk | -sdk) shift ;;
  
negative.code:   '';
  
    xcode-select = writeText "xcode-select" ''
  #!${stdenv.shell}
  while [ $# -gt 0 ]; do
     case "$1" in
           -h | --help) ;; # noop
  