build: add nix package and docs in nix flake

Author: Andreas Hindborg

flake.nix

@@ -1,3 +1,28 @@
+# To use get a shell ready to build the website run `nix develop`.
+#
+# To set up automatic rendering of the HTML in the development shell, run:
+#
+# python3 pre.py
+# mdbook watch
+#
+# If you also want to serve the HTML from a local webserver, run
+#
+# python3 pre.py
+# mdbook serve
+#
+# To build the book:
+#
+# nix build .\#default
+#
+# The build artifacts are available through the symlink `result` in the current
+# working directory directory.
+#
+# Note: flakes and the `nix` command are experimental and must be enabled
+# explicitly [1][2]. Also see the NixOS Wiki entry on flakes [3].
+#
+# [1] https://nix.dev/manual/nix/2.17/contributing/experimental-features#xp-feature-nix-command
+# [2] https://nix.dev/manual/nix/2.17/contributing/experimental-features#xp-feature-flakes
+# [3] https://nixos.wiki/wiki/Flakes
 
 {
   description = "Shell for building rust-for-linux.com";
@@ -14,12 +39,26 @@
       system:
       let
         pkgs = nixpkgs.legacyPackages.${system};
-      in
-      {
-        devShells.default = pkgs.mkShell { packages = with pkgs; [
+        buildDeps = with pkgs; [
           python3
           mdbook
-        ]; };
+        ];
+      in
+      {
+        devShells.default = pkgs.mkShell { packages = buildDeps; };
+        packages.default = pkgs.stdenv.mkDerivation {
+          name = "rust-for-linux.com";
+          nativeBuildInputs = buildDeps;
+          src = ./.;
+          buildPhase = ''
+            python3 pre.py
+            mdbook build
+            python3 post.py
+          '';
+          installPhase = ''
+            cp -r book $out
+          '';
+        };
       }
     );
 }