fix: add shell nix (#1382)

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Fixes RVT-3953
## Changes

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shell.nix

@@ -0,0 +1,71 @@
+# Cross-platform Rust Setup: https://zeroes.dev/p/nix-recipe-for-rust/
+
+let
+	# Pull new Rust packages
+	moz_overlay = import (builtins.fetchTarball https://github.com/mozilla/nixpkgs-mozilla/archive/9b11a87c0cc54e308fa83aac5b4ee1816d5418a2.tar.gz);
+
+	# Overlay package
+	pkgs = import (fetchTarball {
+		url = "https://github.com/NixOS/nixpkgs/archive/refs/tags/23.05.tar.gz";
+	}) { overlays = [ moz_overlay ]; };
+in
+	pkgs.mkShell {
+		name = "rivet";
+
+		buildInputs = with pkgs; [
+			# Tools
+			cloc
+			curl
+			docker-client  # Standardize client CLI since older clients have breaking changes
+			git-lfs
+			jq
+			openssh  # ssh-keygen
+
+			python310Packages.detect-secrets
+
+			# Compilers
+			clang
+			llvm
+			lld
+			pkg-config
+			pkgs.latest.rustChannels.stable.rust
+
+			# Libraries
+			openssl
+
+			# Autocomplete
+			bashInteractive
+			bash-completion
+
+			# Utilities
+			netcat
+
+			# Fixes "cannot change locale" warning
+			glibcLocales
+		]
+			++ extraInputs
+			++ (
+				pkgs.lib.optionals stdenv.isDarwin [
+					libiconv  # See https://stackoverflow.com/a/69732679
+					darwin.apple_sdk.frameworks.Security
+					darwin.apple_sdk.frameworks.CoreServices
+					darwin.apple_sdk.frameworks.CoreFoundation
+					darwin.apple_sdk.frameworks.Foundation
+				]
+			);
+		shellHook = ''
+			# Setup Git LFS
+			git lfs install --manual > /dev/null
+			
+			# Install autocomplete
+			source ${pkgs.bash-completion}/share/bash-completion/bash_completion
+
+			# Fix dynamic library path to fix issue with Python
+			export LD_LIBRARY_PATH="${pkgs.clang}/resource-root/lib:${pkgs.lib.strings.makeLibraryPath [ pkgs.openssl ]}"
+
+			# Set default Rust flags to match the Rust flags used inside of Bolt.
+			#
+			# If these don't match, then the build cache is purged any time Rust is ran from Bolt.
+			export RUSTFLAGS="--cfg tokio_unstable"
+		'';
+	}