feat: add nix flake with rust-overlay for reproducible builds

- Add flake.nix with oxalica/rust-overlay for consistent Rust toolchain
- Add package.nix using cargoLock for dependency management
- Add overlay.nix exposing rustToolchain and freenet-shared package
- Fix build.rs to remove CARGO_BUILD_TARGET for native tool builds

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: mkg20001

deploy-tool/build.rs

@@ -43,6 +43,7 @@ fn main() {
     let status = Command::new(env::var("CARGO").unwrap_or_else(|_| "cargo".into()))
         .env("CARGO_TARGET_DIR", &nested_target_dir)
         .env_remove("CARGO_ENCODED_RUSTFLAGS")
+        .env_remove("CARGO_BUILD_TARGET")
         .args([
             "build",
             "--release",

flake.lock

@@ -0,0 +1,40 @@
+{
+  description = "Freenet shared tools";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+    flake-utils.url = "github:numtide/flake-utils";
+    rust-overlay = {
+      url = "github:oxalica/rust-overlay";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
+  };
+
+  outputs = { self, nixpkgs, flake-utils, rust-overlay }:
+    flake-utils.lib.eachDefaultSystem (system:
+      let
+        pkgs = import nixpkgs {
+          inherit system;
+          overlays = [
+            rust-overlay.overlays.default
+            self.overlays.default
+          ];
+        };
+      in
+      {
+        packages = {
+          freenet-shared = pkgs.freenet-shared;
+          default = pkgs.freenet-shared;
+        };
+
+        devShells.default = pkgs.mkShell {
+          inputsFrom = [ pkgs.freenet-shared ];
+          packages = [
+            pkgs.rustToolchain
+          ];
+        };
+      }
+    ) // {
+      overlays.default = import ./overlay.nix;
+    };
+}

flake.nix

@@ -0,0 +1,8 @@
+final: prev: {
+  rustToolchain = final.rust-bin.stable.latest.default.override {
+    extensions = [ "rust-src" "rust-analyzer" ];
+    targets = [ "wasm32-unknown-unknown" ];
+  };
+
+  freenet-shared = final.callPackage ./package.nix { };
+}

overlay.nix

@@ -0,0 +1,31 @@
+{
+  lib,
+  makeRustPlatform,
+  rustToolchain,
+}:
+
+let
+  rustPlatform = makeRustPlatform {
+    cargo = rustToolchain;
+    rustc = rustToolchain;
+  };
+in
+rustPlatform.buildRustPackage {
+  pname = "freenet-shared";
+  version = "0.1.0";
+
+  src = lib.cleanSource ./.;
+
+  cargoLock = {
+    lockFile = ./Cargo.lock;
+  };
+
+  # Only build the native binary tools, not the WASM contract
+  cargoBuildFlags = [ "-p" "deploy-tool" "-p" "web-container-tool" ];
+
+  meta = with lib; {
+    description = "Freenet shared tools";
+    license = licenses.mit;
+    maintainers = [ ];
+  };
+}