flake.*: add Nix support for establishing a development environment

Nix is a package system similar to Go modules for creating predictable
builds and environments. Nix builds are reproducible and a ligthweight
alternative to Docker.

This change makes the repository a Nix flake that includes a development
environment. Use it with Nix 2.4 and later with flakes enabled:

$ alias nix='nix --extra-experimental-features "nix-command flakes"'
$ nix develop

Signed-off-by: Elias Naur <[email protected]>

Author: eliasnaur

README.md

@@ -23,19 +23,27 @@ This repository contains the open source Tailscale Android client.
 SDK](https://developer.android.com/studio/releases/platform-tools), 
 the [Android NDK](https://developer.android.com/ndk) are required.
 
-```
+```sh
 $ make tailscale-debug.apk
 $ adb install -r tailscale-debug.apk
 ```
 
 The `dockershell` target builds a container with the necessary
 dependencies and runs a shell inside it.
 
-```
+```sh
 $ make dockershell
 # make tailscale-debug.apk
 ```
 
+If you have Nix 2.4 or later installed, a Nix development environment can
+be set up with
+
+```sh
+$ alias nix='nix --extra-experimental-features "nix-command flakes"'
+$ nix develop
+```
+
 Use `make tag_release` to bump the Android version code, update the version
 name, and tag the current commit.
 

flake.lock

@@ -0,0 +1,58 @@
+{
+  description = "Tailscale build environment";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs";
+    android.url = "github:tadfisher/android-nixpkgs";
+    android.inputs.nixpkgs.follows = "nixpkgs";
+  };
+
+  outputs = { self, nixpkgs, android }:
+    let
+      supportedSystems = [ "x86_64-linux" "x86_64-darwin" "aarch64-darwin" ];
+      forAllSystems = f: nixpkgs.lib.genAttrs supportedSystems (system: f system);
+    in
+    {
+      devShells = forAllSystems
+        (system:
+          let
+            pkgs = import nixpkgs {
+              inherit system;
+            };
+            android-sdk = android.sdk.${system} (sdkPkgs: with sdkPkgs;
+              [
+                build-tools-30-0-2
+                cmdline-tools-latest
+                platform-tools
+                platforms-android-31
+                platforms-android-30
+                ndk-23-1-7779620
+                patcher-v4
+              ]);
+          in
+          {
+            default = (with pkgs; buildFHSUserEnv {
+              name = "tailscale";
+              profile = ''
+                export ANDROID_SDK_ROOT="${android-sdk}/share/android-sdk"
+                export JAVA_HOME="${jdk8.home}"
+              '';
+              targetPkgs = pkgs: with pkgs; [
+                android-sdk
+                jdk8
+                clang
+              ] ++ (if stdenv.isLinux then [
+                vulkan-headers
+                libxkbcommon
+                wayland
+                xorg.libX11
+                xorg.libXcursor
+                xorg.libXfixes
+                libGL
+                pkgconfig
+              ] else [ ]);
+            }).env;
+          }
+        );
+    };
+}