deps: Add Nix flake for project dependencies (#124)

This flake includes all deps for building "zisk" and related projects.

To use it, install Nix package manager by following this guide and call nix develop.
Afterwards, use your normal workflow in this environment, e.g. cargo build.

I've tested this on ArchLinux and OSX and it should also work on other Linux flavors.

book/getting_started/install.md

@@ -14,6 +14,21 @@
 sudo apt-get install -y xz-utils jq curl git build-essential qemu-system libomp-dev libgmp-dev nlohmann-json3-dev protobuf-compiler uuid-dev libgrpc++-dev libsecp256k1-dev libsodium-dev libpqxx-dev nasm
 ```
 
+### Nix Flake
+
+Alternatively, you can use [Nix package manager](https://github.com/NixOS/nix) to install all dependencies. First, follow the [guide to install Nix](https://determinate.systems/nix/) on your OS.
+
+Afterwards, use `flake.nix` in `zisk` repository to load the development environment with:
+```
+nix develop
+
+# You can also use a custom shell: 
+nix develop -c zsh
+```
+
+This will start a new shell with correctly set `PATH` and `LD_LIBRARY_PATH` for dependencies necessary to build the project.
+You can exit this shell with Ctrl+D.
+
 ### OSX prerequisites
 ```bash
 # Install brew first.

book/getting_started/quickstart.md

@@ -130,7 +130,7 @@ cd zisk
 
 ### Compile the PIl2 Stark C++ Library (run only once):
 ```bash
-(cd ../pil2-proofman/pil2-stark && git submodule init && git submodule update && make clean && make -j starks_lib && make -j bctree) && export RUSTFLAGS="-L native=$PWD/../pil2-proofman/pil2-stark/lib"
+(cd ../pil2-proofman/pil2-stark && git submodule init && git submodule update && make clean && make -j starks_lib && make -j bctree) && export RUSTFLAGS=$RUSTFLAGS" -L native=$PWD/../pil2-proofman/pil2-stark/lib"
 ```
 
 ### Generate PIL-Helpers Rust Code
@@ -164,4 +164,4 @@ To generate the proof, the following command needs to be run.
 ```bash
 (cd ../pil2-stark-js && npm i) 
 node ../pil2-stark-js/src/main_verifier.js -v build/provingKey/zisk/final/final.verkey.json -s build/provingKey/zisk/final/final.starkinfo.json -i build/provingKey/zisk/final/final.verifierinfo.json -o proofs/proofs/final_proof.json -b proofs/publics.json
-```
+```

flake.nix

@@ -0,0 +1,41 @@
+{
+  description = "A flake with project build dependencies";
+  inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
+  inputs.systems.url = "github:nix-systems/default";
+  inputs.flake-utils = {
+    url = "github:numtide/flake-utils";
+    inputs.systems.follows = "systems";
+  };
+
+  outputs = { self, nixpkgs, flake-utils, ... }:
+    flake-utils.lib.eachDefaultSystem (system:
+      let
+        pkgs = import nixpkgs {
+          inherit system;
+          config.allowUnfreePredicate = pkg:
+            builtins.elem (nixpkgs.lib.getName pkg) [ "mkl" ];
+        };
+      in {
+        devShells.default = pkgs.mkShell {
+          packages = [
+            pkgs.grpc
+            pkgs.gmp
+            pkgs.jq
+            pkgs.libsodium
+            pkgs.libpqxx
+            pkgs.libuuid
+            pkgs.openssl
+            pkgs.postgresql
+            pkgs.protobuf
+            pkgs.secp256k1
+            pkgs.nlohmann_json
+            pkgs.nasm
+            pkgs.libgit2
+          ] ++ (pkgs.lib.optionals pkgs.stdenv.isLinux [ pkgs.mkl ])
+            ++ (pkgs.lib.optionals pkgs.stdenv.isDarwin
+              [ pkgs.darwin.apple_sdk.frameworks.Security ]);
+
+          RUSTFLAGS = (builtins.map (a: "-L ${a}/lib") [ pkgs.libgit2 ]);
+        };
+      });
+}