chore: add nix flake

Author: meh

flake.lock

@@ -0,0 +1,28 @@
+{
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
+    utils.url = "github:numtide/flake-utils";
+    fenix = {
+      url = "github:nix-community/fenix";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
+  };
+
+  outputs = { self, utils, nixpkgs, fenix, }: utils.lib.eachDefaultSystem (system: let 
+    pkgs = nixpkgs.legacyPackages.${system};
+    rust = fenix.packages.${system};
+    lib = pkgs.lib;
+  in {
+    devShell = pkgs.mkShell {
+      buildInputs = with pkgs; with llvmPackages; [
+        # For building.
+        clang rust.latest.toolchain pkg-config openssl libsodium libclang.lib
+      ];
+
+      LIBCLANG_PATH = "${pkgs.llvmPackages.libclang.lib}/lib";
+      RUST_BACKTRACE = 1;
+      # RUST_LOG = "info,sqlx::query=warn";
+      RUSTFLAGS = "-C target-cpu=native";
+    };
+  });
+}