add nix files

nix/river.nix

@@ -0,0 +1,39 @@
+{ pkgs ? import <nixpkgs> {} }:
+
+pkgs.stdenv.mkDerivation rec {
+  pname = "river";
+  version = "master";
+
+  src = ./.;
+  # src = builtins.fetchGit {
+  #   url = "https://github.com/ifreund/river";
+  #   ref = "master";
+  # };
+
+  nativeBuildInputs = with pkgs; [
+    pkg-config
+  ];
+
+  buildInputs = with pkgs; [
+    zig
+    wayland
+    wayland-protocols
+    wlroots
+    libxkbcommon
+    pixman
+    libudev
+    xorg.libX11
+    libGL
+    libevdev
+    scdoc
+  ];
+
+  buildPhase = ''
+    export HOME=$TMPDIR
+    zig build -Drelease-safe -Dxwayland -Dman-pages
+  '';
+
+  installPhase = ''
+    zig build -Drelease-safe -Dxwayland -Dman-pages --prefix $out install
+  '';
+}