Add minimal support for NixOS buildsystem (#134)

README.md

@@ -91,3 +91,15 @@ library on your machine under `/usr/local`.
 After running the script to install system dependencies, build the project with stack: 
 
     stack test
+
+## Build on NixOS
+
+`tools/userchroot.nix` expression contains definitions to open
+chroot-environment containing necessary dependencies. Type
+
+    $ nix-shell tools/userchroot.nix
+    $ stack build --system-ghc
+
+to enter the environment and build the project. Note, that it is an emulation
+of common Linux environment rather than full-featured Nix package expression.
+No exportable Nix package will appear, but local development is possible.

tools/userchroot.nix

@@ -0,0 +1,66 @@
+#
+# This script is provided by @grwlf (grwlf@gmail.com) and is supported on best
+# effort basis.  TensorFlow development team does not regularly test this script
+# and can't answer any questions about it.
+#
+{ pkgs ? import <nixpkgs> {} }:
+
+with pkgs;
+
+let
+  tensorflow-c = stdenv.mkDerivation {
+
+    name = "tensorflow-c";
+
+    src = fetchurl {
+      url = "https://storage.googleapis.com/tensorflow/libtensorflow/libtensorflow-cpu-linux-x86_64-1.0.0.tar.gz";
+      sha256 = "1kmss9wdri5ibd19b4ymh2dvajw5cy34bxzxlaa5i60hiwpppljy";
+    };
+
+    buildCommand = ''
+      . $stdenv/setup
+      mkdir -pv $out
+      tar -C $out -xzf $src
+    '';
+  };
+
+  fhs = pkgs.buildFHSUserEnv {
+    name = "fhs";
+    targetPkgs = pkgs:
+      with pkgs.python3Packages;
+      with pkgs.haskellPackages;
+      with pkgs;
+      assert stack.version >= "1.4";
+      assert ghc.version >= "8";
+      [
+        snappy
+        snappy.dev
+        protobuf3_2
+        stack
+        ghc
+        iana-etc
+        pkgs.zlib
+        pkgs.zlib.dev
+        tensorflow-c
+        gcc
+        gdb
+      ];
+    runScript = "bash";
+    profile = ''
+      export USE_CCACHE=1
+      export LIBRARY_PATH=/usr/lib64
+      export LD_LIBRARY_PATH=$(pwd):/usr/lib64
+      export ACLOCAL_PATH=/usr/share/aclocal
+      export LANG=C
+      export LC_ALL=en_US.utf-8
+      export PATH="$HOME/.local/bin:$PATH"
+    '';
+  };
+
+in
+stdenv.mkDerivation {
+  name = fhs.name + "-env";
+  nativeBuildInputs = [ fhs ];
+  shellHook = "exec fhs";
+}
+