Make build script NixOS-compatible

build.sh

@@ -1,3 +1,12 @@
-#!/bin/bash
+#!/usr/bin/env bash
+SCRIPT_DIR=`dirname "$0"`
+if command -v nix-shell &> /dev/null; then
+	# If in NixOS use shell.nix
+	nix-shell --pure $SCRIPT_DIR/shell.nix --run "cd $SCRIPT_DIR && hugo"
+else
+	# Otherwise use global hugo
+	DIR=$PWD
+	cd $SCRIPT_DIR
 	hugo
-#find public -name '*.html' -type f -exec tidy --quiet yes --drop-empty-elements no --hide-comments yes -mq '{}' \; &> /dev/null
+	cd $DIR
+fi