Added shell.nix to create dev environment (#3362)

CODEOWNERS

@@ -1,2 +1,4 @@
 # yale-mistakes were made
 /pykanidm/* @yaleman
+# Least qualified nix guy :P
+shell.nix @cebbinghaus

rust-toolchain.toml

@@ -0,0 +1,2 @@
+[toolchain]
+channel = "stable"

shell.nix

@@ -0,0 +1,25 @@
+{ pkgs ? import <nixpkgs> {} }:
+	let
+	overrides = (builtins.fromTOML (builtins.readFile ./rust-toolchain.toml));
+in
+pkgs.mkShellNoCC rec {
+	# Kanidm dependencies
+	buildInputs = with pkgs; [
+		pkg-config
+		
+		cargo
+		rustc
+
+		clang
+		llvmPackages.bintools
+		
+		openssl
+	] ++ pkgs.lib.optionals (pkgs.stdenv.isLinux) [
+		systemd
+		linux-pam
+	];
+	
+	RUSTC_VERSION = overrides.toolchain.channel;
+	# https://github.com/rust-lang/rust-bindgen#environment-variables
+	LIBCLANG_PATH = pkgs.lib.makeLibraryPath [ pkgs.llvmPackages_latest.libclang.lib ];
+}