add packages to Nix flake config, move to repo root

This way we can actually build and run a node using just:
```sh
nix run 'github:status-im/nimbus-eth2?submodules=1'
```
The `?submodules=1` part should eventually not be necessary.
For more details see:
NixOS/nix#4423

Signed-off-by: Jakub Sokołowski <jakub@status.im>

.github/workflows/ci.yml

@@ -238,7 +238,7 @@ jobs:
         if: ${{ !cancelled() }} && github.event_name == 'pull_request'
         run: |
           excluded_files="config.yaml"
-          excluded_extensions="ans|cfg|json|json\\.template|md|png|service|ssz|txt"
+          excluded_extensions="ans|cfg|json|json\\.template|md|png|service|ssz|txt|lock|nix"
 
           current_year=$(date +"%Y")
           problematic_files=()

.gitignore

@@ -1,5 +1,5 @@
 # beacon_chain
-# Copyright (c) 2018-2023 Status Research & Development GmbH
+# Copyright (c) 2018-2024 Status Research & Development GmbH
 # Licensed and distributed under either of
 #   * MIT license (license terms in the root directory or at http://opensource.org/licenses/MIT).
 #   * Apache v2 license (license terms in the root directory or at http://www.apache.org/licenses/LICENSE-2.0).
@@ -65,6 +65,7 @@ geth-*.zip
 # generated during Nim compilation
 *.nim.generated.nim
 
+result
 /dist
 /benchmark_results
 /.update.timestamp

ci/Jenkinsfile.nix

@@ -0,0 +1,85 @@
+#!/usr/bin/env groovy
+/* beacon_chain
+ * Copyright (c) 2019-2024 Status Research & Development GmbH
+ * Licensed and distributed under either of
+ *   * MIT license (license terms in the root directory or at https://opensource.org/licenses/MIT).
+ *   * Apache v2 license (license terms in the root directory or at https://www.apache.org/licenses/LICENSE-2.0).
+ * at your option. This file may not be copied, modified, or distributed except according to those terms.
+ */
+library 'status-jenkins-lib@nix/flake-build'
+
+pipeline {
+  /* This way we run the same Jenkinsfile on different platforms. */
+  agent { label params.AGENT_LABEL }
+
+  parameters {
+    string(
+      name: 'AGENT_LABEL',
+      description: 'Label for targetted CI slave host: linux/macos',
+      defaultValue: params.AGENT_LABEL ?: getAgentLabel(),
+    )
+    choice(
+      name: 'VERBOSITY',
+      description: 'Value for the V make flag to increase log verbosity',
+      choices: [0, 1, 2]
+    )
+  }
+
+  options {
+    timestamps()
+    ansiColor('xterm')
+    /* This also includes wait time in the queue. */
+    timeout(time: 1, unit: 'HOURS')
+    /* Limit builds retained. */
+    buildDiscarder(logRotator(
+      numToKeepStr: '5',
+      daysToKeepStr: '30',
+    ))
+    /* Abort old builds for non-main branches. */
+    disableConcurrentBuilds(
+      abortPrevious: !isMainBranch()
+    )
+  }
+
+  stages {
+    stage('Beacon Node') {
+      steps { script {
+        nix.flake('beacon_node')
+      } }
+    }
+
+    stage('Version check') {
+      steps { script {
+        sh 'result/bin/nimbus_beacon_node --version'
+      } }
+    }
+  }
+
+  post {
+    always {
+      cleanWs(
+        disableDeferredWipeout: true,
+        deleteDirs: true
+      )
+    }
+  }
+}
+
+def isMainBranch() {
+  return ['stable', 'testing', 'unstable'].contains(env.BRANCH_NAME)
+}
+
+/* This allows us to use one Jenkinsfile and run
+ * jobs on different platforms based on job name. */
+def getAgentLabel() {
+    if (params.AGENT_LABEL) { return params.AGENT_LABEL }
+    /* We extract the name of the job from currentThread because
+     * before an agent is picket env is not available. */
+    def tokens = Thread.currentThread().getName().split('/')
+    def labels = []
+    /* Check if the job path contains any of the valid labels. */
+    ['linux', 'macos', 'x86_64', 'aarch64', 'arm64'].each {
+        if (tokens.contains(it)) { labels.add(it) }
+    }
+    return labels.join(' && ')
+}

flake.nix

@@ -0,0 +1,38 @@
+{
+  description = "nimbus-eth2";
+
+  inputs.nixpkgs.url = github:NixOS/nixpkgs/master;
+
+  outputs = { self, nixpkgs }:
+    let
+      stableSystems = [
+        "x86_64-linux" "aarch64-linux" "armv7a-linux"
+        "x86_64-darwin" "aarch64-darwin"
+        "x86_64-windows"
+      ];
+      forEach = nixpkgs.lib.genAttrs;
+      forAllSystems = forEach stableSystems;
+      pkgsFor = forEach stableSystems (
+        system: import nixpkgs { inherit system; }
+      );
+    in rec {
+      packages = forAllSystems (system: let
+        buildTarget = pkgsFor.${system}.callPackage ./nix/default.nix {
+          inherit stableSystems; src = self;
+        };
+        build = targets: buildTarget.override { inherit targets; };
+      in rec {
+        beacon_node      = build ["nimbus_beacon_node"];
+        signing_node     = build ["nimbus_signing_node"];
+        validator_client = build ["nimbus_validator_client"];
+        ncli             = build ["ncli"];
+        ncli_db          = build ["ncli_db"];
+
+        default = beacon_node;
+      });
+
+      devShells = forAllSystems (system: {
+        default = pkgsFor.${system}.callPackage ./nix/shell.nix { };
+      });
+    };
+}

nix/README.md

@@ -0,0 +1,29 @@
+# Usage
+
+## Shell
+
+A development shell can be started using:
+```sh
+nix develop
+```
+
+## Building
+
+To build a beacon node you can use:
+```sh
+nix build '.?submodules=1#beacon_node'
+```
+The `?submodules=1` part should eventually not be necessary.
+For more details see:
+https://github.com/NixOS/nix/issues/4423
+
+It can be also done without even cloning the repo:
+```sh
+nix build 'github:status-im/nimbus-eth2?submodules=1'
+```
+
+## Running
+
+```sh
+nix run 'github:status-im/nimbus-eth2?submodules=1'
+```

nix/csources.nix

@@ -0,0 +1,12 @@
+{ pkgs ? import <nixpkgs> { } }:
+
+let
+  tools = pkgs.callPackage ./tools.nix {};
+  sourceFile = ../vendor/nimbus-build-system/vendor/Nim/config/build_config.txt;
+in pkgs.fetchFromGitHub {
+  owner = "nim-lang";
+  repo = "csources_v1";
+  rev = tools.findKeyValue "^nim_csourcesHash=([a-f0-9]+)$" sourceFile;
+  # WARNING: Requires manual updates when Nim compiler version changes.
+  hash = "sha256-gwBFuR7lzO4zttR/6rgdjXMRxVhwKeLqDwpmOwMyU7A=";
+}

nix/default.nix

@@ -0,0 +1,91 @@
+{
+  pkgs ? import <nixpkgs> { },
+  # Source code of this repo.
+  src ? ../.,
+  # Options: nimbus_light_client, nimbus_validator_client, nimbus_signing_node, all
+  targets ? ["nimbus_beacon_node"],
+  # Options: 0,1,2
+  verbosity ? 0,
+  # Perform 2-stage bootstrap instead of 3-stage to save time.
+  quickAndDirty ? true,
+  # These are the only platforms tested in CI and considered stable.
+  stableSystems ? [
+    "x86_64-linux" "aarch64-linux" "armv7a-linux"
+    "x86_64-darwin" "aarch64-darwin"
+    "x86_64-windows"
+  ],
+}:
+
+let
+  inherit (pkgs) stdenv lib writeScriptBin callPackage;
+
+  nimble = callPackage ./nimble.nix {};
+  csources = callPackage ./csources.nix {};
+  revision = lib.substring 0 8 (src.rev or "dirty");
+in stdenv.mkDerivation rec {
+  pname = "nimbus-eth2";
+  version = "${callPackage ./version.nix {}}-${revision}";
+
+  inherit src;
+
+  # Fix for Nim compiler calling 'git rev-parse' and 'lsb_release'.
+  nativeBuildInputs = let
+    fakeGit = writeScriptBin "git" "echo ${version}";
+    fakeLsbRelease = writeScriptBin "lsb_release" "echo nix";
+  in
+    with pkgs; [ fakeGit fakeLsbRelease which cmake ]
+    ++ lib.optionals stdenv.isDarwin [ pkgs.darwin.cctools ];
+
+  enableParallelBuilding = true;
+
+  # Disable CPU optmizations that make binary not portable.
+  NIMFLAGS = "-d:disableMarchNative -d:git_revision_override=${revision}";
+  # Avoid Nim cache permission errors.
+  XDG_CACHE_HOME = "/tmp";
+
+  makeFlags = targets ++ [
+    "V=${toString verbosity}"
+    # TODO: Compile Nim in a separate derivation to save time.
+    "QUICK_AND_DIRTY_COMPILER=${if quickAndDirty then "1" else "0"}"
+    "QUICK_AND_DIRTY_NIMBLE=${if quickAndDirty then "1" else "0"}"
+  ];
+
+  # Generate the nimbus-build-system.paths file.
+  configurePhase = ''
+    patchShebangs scripts vendor/nimbus-build-system > /dev/null
+    make nimbus-build-system-paths
+  '';
+
+  # Avoid nimbus-build-system invoking `git clone` to build Nim.
+  preBuild = ''
+    pushd vendor/nimbus-build-system/vendor/Nim
+    mkdir dist
+    cp -r ${nimble} dist/nimble
+    cp -r ${csources} csources_v1
+    chmod 777 -R dist/nimble csources_v1
+    sed -i 's/isGitRepo(destDir)/false/' tools/deps.nim
+    popd
+  '';
+
+  installPhase = ''
+    mkdir -p $out/bin
+    rm -f build/generate_makefile
+    cp build/* $out/bin
+  '';
+
+  meta = with lib; {
+    homepage = "https://nimbus.guide/";
+    downloadPage = "https://github.com/status-im/nimbus-eth2/releases";
+    changelog = "https://github.com/status-im/nimbus-eth2/blob/stable/CHANGELOG.md";
+    description = "Nimbus is a lightweight client for the Ethereum consensus layer";
+    longDescription = ''
+      Nimbus is an extremely efficient consensus layer client implementation.
+      While it's optimised for embedded systems and resource-restricted devices --
+      including Raspberry Pis, its low resource usage also makes it an excellent choice
+      for any server or desktop (where it simply takes up fewer resources).
+    '';
+    license = with licenses; [asl20 mit];
+    mainProgram = "nimbus_beacon_node";
+    platforms = stableSystems;
+  };
+}