anchor.diff: -{ lib, stdenv, version, fetch, fetchpatch, cmake, llvm, libcxx
  +{ lib, stdenv, version, fetch, fetchpatch, cmake, llvm
   , enableShared ? !stdenv.hostPlatform.isStatic
   }:
   
  
positive.code:     })
    ];
  
    nativeBuildInputs = [ cmake llvm.dev ];
  
    cmakeFlags = lib.optionals (!enableShared) [
      "-DLIBUNWIND_ENABLE_SHARED=OFF"
    ] ++ lib.optionals (stdenv.hostPlatform.useLLVM or false) [
      "-DLIBUNWIND_HAS_NOSTDINCXX_FLAG=ON"
      "-DLLVM_ENABLE_LIBCXX=ON"
    ];
  }
  
negative.code:   inherit version;
  
    src = fetch "libunwind" "035dsxs10nyiqd00q07yycvmkjl01yz4jdlrjvmch8klxg4pyjhp";
  
    postUnpack = ''
      unpackFile ${llvm.src}
      cmakeFlagsArray=($cmakeFlagsArray -DLLVM_PATH=$PWD/$(ls -d llvm-*))
    '';
  
    patches = [
      ./gnu-install-dirs.patch
  