blueline: Add extract-files.sh helper script

Change-Id: Ie5f4c6ab8debf1a2b11db45b0cb6957e2539ac80

extract-files.sh

+#!/bin/bash
+#
+# Copyright (C) 2016 The CyanogenMod Project
+# Copyright (C) 2017-2020 The LineageOS Project
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+
+set -e
+
+MY_DIR="$(cd "$(dirname "${0}")"; pwd -P)"
+
+"${MY_DIR}/../crosshatch/blueline/extract-files.sh" "$@"