anchor.diff:  
       export PATH=$(pwd)/bin:$PATH
   
  -    ${lib.optionalString (stdenv.buildPlatform != stdenv.targetPlatform) ''
  +    ${lib.optionalString isCross ''
       # Independent from host/target, CC should produce code for the building system.
       # We only set it when cross-compiling.
       export CC=${buildPackages.stdenv.cc}/bin/cc
  
positive.code:   # We need a target compiler which is still runnable at build time,
    # to handle the cross-building case where build != host == target
    targetCC = pkgsBuildTarget.targetPackages.stdenv.cc;
  in
  
  stdenv.mkDerivation rec {
  
negative.code: , buildPackages
  , pkgsBuildTarget
  , callPackage
  , threadsCross ? null # for MinGW
  }:
  
  # threadsCross is just for MinGW
  assert threadsCross != null -> stdenv.targetPlatform.isWindows;
  
  let
    go_bootstrap = buildPackages.callPackage ./bootstrap.nix { };
  