scripts: add 'BOM' update script

Need this script when we add external dependencies.

Signed-off-by: Gyu-Ho Lee <gyuhox@gmail.com>

scripts/updatebom.sh

@@ -0,0 +1,28 @@
+#!/usr/bin/env bash
+
+set -e
+
+if ! [[ "$0" =~ "scripts/updatebom.sh" ]]; then
+	echo "must be run from repository root"
+	exit 255
+fi
+
+echo "installing 'bill-of-materials.json'"
+go get -v -u github.com/coreos/license-bill-of-materials
+
+echo "setting up GOPATH"
+rm -rf ./gopath
+mkdir ./gopath
+mv ./cmd/vendor ./gopath/src
+
+echo "generating bill-of-materials.json"
+GOPATH=`pwd`/gopath license-bill-of-materials \
+    --override-file ./bill-of-materials.override.json \
+    github.com/coreos/etcd github.com/coreos/etcd/etcdctl > bill-of-materials.json
+
+echo "reverting GOPATH,vendor"
+mv ./gopath/src ./cmd/vendor
+rm -rf ./gopath
+
+echo "generated bill-of-materials.json"
+