feat: add Nix flake

.gitignore

@@ -3,3 +3,6 @@ dist/
 /compile_commands.json
 
 .cache/
+
+# nix build result
+result

flake.nix

@@ -0,0 +1,46 @@
+{
+  inputs = {
+    flake-utils.url = "github:numtide/flake-utils";
+    nixpkgs.url = "github:nixos/nixpkgs?ref=nixos-unstable";
+  };
+  outputs =
+    { flake-utils, nixpkgs, ... }:
+    flake-utils.lib.eachDefaultSystem (
+      system:
+      let
+        pkgs = import nixpkgs { inherit system; };
+
+        name = "LiDM";
+        version = "0.0.1";
+
+        lidm = (
+          pkgs.stdenv.mkDerivation {
+            pname = name;
+            version = version;
+
+            src = ./.;
+
+            nativeBuildInputs = with pkgs; [
+              gcc
+              gnumake
+              linux-pam
+            ];
+
+            makeFlags = [
+              "DESTDIR=$(out)"
+              "PREFIX="
+            ];
+
+            fixupPhase = ''
+              rm -rf $out/etc
+            '';
+          }
+        );
+      in
+      rec {
+        defaultApp = flake-utils.lib.mkApp { drv = defaultPackage; };
+        defaultPackage = lidm;
+        devShell = pkgs.mkShell { buildInputs = lidm.nativeBuildInputs ++ [ pkgs.clang-tools ]; };
+      }
+    );
+}