anchor.diff:  
     libzbar_name =
       if stdenv.isLinux then "libzbar.so.0"
  +    else if stdenv.isDarwin then "libzbar.0.dylib"
       else "libzbar${stdenv.hostPlatform.extensions.sharedLibrary}";
   
     # Not provided in official source releases, which are what upstream signs.
  
positive.code: 
    src = fetchurl {
      url = "https://download.electrum.org/${version}/Electrum-${version}.tar.gz";
      sha256 = "sha256-ucLLfqmTKO5Qpg+PnmcdQwht7cWMWJoFjQWnDecEtVs=";
    };
  
    postUnpack = ''
  
negative.code:   ];
  
    preBuild = ''
      substituteInPlace ./electrum/ecc_fast.py \
        --replace ${libsecp256k1_name} ${secp256k1}/lib/libsecp256k1${stdenv.hostPlatform.extensions.sharedLibrary}
    '' + (if enableQt then ''
  