nix-shell config for rust/substrate development on macos

rust.nix

let
  moz_overlay = import (builtins.fetchTarball https://github.com/mozilla/nixpkgs-mozilla/archive/master.tar.gz);
  nixpkgs = import <nixpkgs> { overlays = [ moz_overlay ]; };
  myrust = (nixpkgs.rustChannelOf { date = "2019-05-21"; channel = "nightly"; }).rust.override { extensions = [ "rust-src" "rust-analysis" "rustfmt-preview" ]; targets = [ "wasm32-unknown-unknown" ];}; 
in
  with nixpkgs;
  stdenv.mkDerivation {
    name = "rust-dev";
    buildInputs = [
      myrust
      rustup
      rustracer
      openssl
      wasm-gc
      cmake
      pkgconfig
      python3
      gnuplot
      wabt
      llvmPackages.clang-unwrapped
    ] ++ lib.optionals stdenv.isDarwin [
      darwin.apple_sdk.frameworks.IOKit
      darwin.apple_sdk.frameworks.Security
      darwin.apple_sdk.frameworks.CoreServices
    ];

    LIBCLANG_PATH="${llvmPackages.libclang}/lib";
    RUST_SRC_PATH="${myrust}/lib/rustlib/src/rust/src";

    shellHook = ''
      export NIX_CXXSTDLIB_LINK=""
      export CARGO_HOME="./.cargo"
    '';
  }