Basic build script (#421)

* Basic build script

Will use this for releasing the first version. Working on basic release docs too.

* Move under build/

.gitignore

@@ -1,9 +1,12 @@
 # Ignore built binaries for the DPT tools, but not similarly-named directories.
-**/policygen
+**/policygen*
 !**/policygen/
 
-**/tfengine
+**/tfengine*
 !**/tfengine/
 
-**/tfimport
+**/tfimport*
 !**/tfimport/
+
+# Ignore bundled templates.
+*.tar.gz

build/build-release.sh

@@ -0,0 +1,65 @@
+# Copyright 2020 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+#!/usr/bin/env bash
+
+# Helper to build release artifacts - binaries, and templates and policies bundles.
+#
+# Usage (from repo root):
+# ./build/build-release.sh -o . -v v0.1.0
+
+set -e
+
+OUTPUT_DIR="."
+VERSION=""
+
+while getopts 'o:v:' opt; do
+  case ${opt} in
+    o) OUTPUT_DIR=${OPTARG} ;;
+    v) VERSION=${OPTARG} ;;
+    *) echo "Invalid flag ${OPTARG}"
+       exit 1
+       ;;
+  esac
+done
+
+if [[ -z ${VERSION} ]]; then
+  echo "-v must be set"
+  exit 1
+fi
+
+version_regex="^v[0-9]+\.[0-9]+\.[0-9]+$"
+if ! [[ ${VERSION} =~ ${version_regex} ]]; then
+  echo "Version \"${VERSION}\" does not match regex ${version_regex}"
+  exit 1
+fi
+
+# Build binaries
+SUPPORTED_OS=("linux" "darwin" "windows")
+SUPPORTED_ARCH=("amd64")
+for OS in "${SUPPORTED_OS[@]}"; do
+  for ARCH in "${SUPPORTED_ARCH[@]}"; do
+    for build_dir in $(find './cmd' -mindepth 1 -maxdepth 1 -type d); do
+      bin="$(basename ${build_dir})_${VERSION}_${OS}-${ARCH}"
+      echo "Building ${OUTPUT_DIR}/${bin}"
+      env GOOS="${OS}" GOARCH="${ARCH}" go build -o "${OUTPUT_DIR}/${bin}" "${build_dir}"
+    done
+  done
+done
+
+echo 'Bundling Engine templates'
+tar -czf "templates_${VERSION}.tar.gz" "templates/tfengine"
+
+echo 'Bundling Policygen policies'
+tar -czf "policies_${VERSION}.tar.gz" "templates/policygen"