feat: added nix flake (#10934)

Adding a Nix flake for a deterministic development environment.

This currently provides only a development shell. To use it, ensure you have Nix installed with experimental features enabled and the nix command available. Then, run nix develop to enter a shell with all OS dependencies needed for development.

Future improvements may include automating build steps as well.






closes: #XXXX
refs: #XXXX

## Description


### Security Considerations


### Scaling Considerations


### Documentation Considerations


### Testing Considerations


### Upgrade Considerations

.github/workflows/nix-check.yml

@@ -0,0 +1,49 @@
+name: Nix Flake Check
+
+on:
+  pull_request:
+  push:
+    branches:
+      - master
+      - 'release-*'
+      - 'dev-*'
+permissions:
+  contents: read
+
+jobs:
+  flake-check:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Install Nix
+        uses: DeterminateSystems/nix-installer-action@v9
+
+      - name: Enable flakes
+        uses: DeterminateSystems/magic-nix-cache-action@v2
+
+      - name: Check Nix flake inputs
+        run: nix flake check
+
+      - name: Show flake metadata
+        if: always() # Run even if previous step fails
+        run: nix flake metadata
+
+      - name: Validate flake outputs
+        if: always() # Run even if previous step fails
+        run: nix flake show
+
+      - name: Check build in Nix dev shell
+        run: |
+          # Enter nix develop and run build commands
+          nix develop --command bash -c '
+            # Install dependencies
+            yarn install
+            
+            # Build the project
+            yarn build
+            
+            # Build cosmic-swingset
+            cd packages/cosmic-swingset && make
+          '

flake.nix

@@ -0,0 +1,75 @@
+{
+  description = "Agoric SDK Development Environment";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+    flake-utils.url = "github:numtide/flake-utils";
+  };
+
+  outputs = { self, nixpkgs, flake-utils }:
+    flake-utils.lib.eachDefaultSystem (system:
+      let
+        pkgs = nixpkgs.legacyPackages.${system};
+               # Custom Node.js 20.9.0 package
+        custom_node_20_9 = pkgs.stdenv.mkDerivation {
+          pname = "nodejs";
+          version = "20.9.0";
+
+          src = pkgs.fetchurl {
+            url = "https://nodejs.org/dist/v20.9.0/node-v20.9.0-${if pkgs.stdenv.isDarwin then "darwin" else "linux"}-${if pkgs.stdenv.isAarch64 then "arm64" else "x64"}.tar.gz";
+            sha256 = if pkgs.stdenv.isDarwin && pkgs.stdenv.isAarch64 then
+              "0snfsz2mmjdavi38nglayw5yia74q9h1xzz2ahpri8yqx1md9lii" # darwin-arm64
+            else if pkgs.stdenv.isDarwin then
+              "1j6cw6i3hjqv8zk1nbsqg560k7rgcmyl9cfd4vlvn5wclzr76nzw" # darwin-x64
+            else if pkgs.stdenv.isAarch64 then
+              "0skah3bal5irvramnfn86vgi0c375ywsyb4xaxmx3gvlnbpdp9yj" # linux-arm64
+            else if (pkgs.stdenv.isLinux && !pkgs.stdenv.isAarch64) then
+              "0q3gy4z5b8dd0w37ya5wlkbv4xhyqa1s0zwh71258x5z5w4rz4gh" # linux-x64
+            else
+              throw "Unsupported system: This derivation only supports Linux (x64/arm64) and Darwin (x64/arm64) systems";
+          };
+
+          installPhase = ''
+              echo "installing nodejs"
+              mkdir -p $out
+              cp -r ./ $out/
+            '';
+
+
+          # Meta information for the package
+          meta = with pkgs.lib; {
+            description = "Node.js 20.9.0 JavaScript runtime";
+            homepage = "https://nodejs.org";
+            license = licenses.mit;
+            platforms = platforms.unix;
+          };
+        };
+      in
+      {
+        devShells.default = pkgs.mkShell {
+          buildInputs = with pkgs; [
+            custom_node_20_9
+            (yarn.override { nodejs = custom_node_20_9; })
+            (python3.withPackages (ps: [ ps.distutils ]))
+            pkg-config
+            go_1_23
+            gopls
+            delve
+            gcc
+            gnumake
+            protobuf
+            buf
+            git
+          ];
+
+          shellHook = ''
+            export PATH=$PATH:$HOME/go/bin
+
+            echo "Node.js $(node --version)"
+            echo "NPM $(npm --version)"
+            echo "Yarn using Node.js $(yarn node -v)"
+          '';
+        };
+      }
+    );
+}