feat(nix): reorganize nix flake for modularity and flexibility

assets/pkg/nix/lidm.nix

@@ -0,0 +1,26 @@
+{ config, pkgs, ...}: pkgs.stdenv.mkDerivation rec {
+    pname = "lidm";
+    version = config.version;
+    src = config.src;
+
+    nativeBuildInputs = with pkgs; [
+        gcc
+        gnumake
+        linux-pam
+    ];
+
+    makeFlags = [
+        "DESTDIR=$(out)"
+        "PREFIX="
+    ];
+
+    installPhase = ''
+        make install DESTDIR=$out PREFIX=
+        mkdir -p $out/etc/systemd/system/
+        make install-service-systemd DESTDIR=$out PREFIX=
+    '';
+
+    fixupPhase = ''
+        rm -rf $out/etc
+    '';
+}