message: Put warning on top of `default.nix`
diff: -# TODO: Download rust version and targets via nix expression instead of rustup.
  +# This is an unsupported development environment, instantly enabling `make build
  +# build-contracts-rs`. There is no official support for this nix derivation.
  #
  -# Enables `make build build-contracts-rs`, not `all`, as we do not include assembly script compiler.
  +# Do not use this, but follow instructions in the `README.md` instead.
  let
  pkgs = import <nixpkgs> { };
  @@ -15,7 +16,6 @@ in pkgs.stdenv.mkDerivation {
  openssl.dev
  protobuf
  - # Dependencies just used in makefile
  which
  rustup
  cargo
  @@ -23,6 +23,7 @@ in pkgs.stdenv.mkDerivation {
  # Required to build openssl
  perl
  ];
  +
  shellHook = ''
  export LD_LIBRARY_PATH=${pkgs.zlib}/lib
  