Add scripts/chroot_build.sh to call build_deb.sh in a chrooted env

Support common debian and ubuntu version, such as jessie, stretch,
trusty, and xenial, etc.

e.g.
$ sudo scripts/chroot_build.sh jessie

scripts/chroot_build.sh

@@ -0,0 +1,125 @@
+#!/bin/sh
+# Copyright 2018 Roger Shimizu <rosh@debian.org>
+#
+# This is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+
+set -e
+
+help_usage() {
+cat << EOT
+
+Call build_deb.sh script in a chrooted environment
+Usage:
+	sudo $(basename $0) [--help|-h] [codename]
+
+	--help|-h	Show this usage.
+	[code name]	Debian/Ubuntu release codename
+			e.g. jessie/stretch/trusty/xenial
+
+EOT
+exit
+}
+
+# POSIX-compliant maint function recommend by devref
+# to check for the existence of a command
+# https://www.debian.org/doc/manuals/developers-reference/ch06.html#bpp-debian-maint-scripts
+pathfind() {
+	OLDIFS="$IFS"
+	IFS=:
+	for p in $PATH; do
+		if [ -x "$p/$*" ]; then
+		IFS="$OLDIFS"
+		return 0
+		fi
+	done
+	IFS="$OLDIFS"
+	return 1
+}
+
+case "$1" in
+wheezy|precise)
+	echo Sorry, the system $1 is not supported.
+	;;
+jessie|stretch|buster|testing|unstable|sid)
+	OSID=debian
+	REPO=http://deb.debian.org/debian
+	;;
+trusty|yakkety|zesty|xenial|artful|bionic)
+	OSID=ubuntu
+	REPO=http://archive.ubuntu.com/ubuntu
+	;;
+--help|-h|*)
+	help_usage
+esac
+
+if ! pathfind debootstrap; then
+	echo Please install debootstrap package.
+	exit 1
+fi
+
+OSVER=$1
+CHROOT=/tmp/${OSVER}-build-$(date +%Y%m%d%H%M)
+TIMESTAMP0=$(date)
+
+mkdir -p ${CHROOT}/etc
+echo en_US.UTF-8 UTF-8 > ${CHROOT}/etc/locale.gen
+if ! debootstrap --variant=minbase --include=ca-certificates,git,sudo,wget,whiptail --exclude=upstart,systemd $OSVER $CHROOT $REPO; then
+	echo debootstrap failed. Please kindly check whether proper sudo or not.
+	exit 1
+fi
+case "$OSID" in
+debian)
+	echo deb $REPO ${OSVER} main > ${CHROOT}/etc/apt/sources.list
+	echo deb $REPO ${OSVER}-updates main >> ${CHROOT}/etc/apt/sources.list
+	echo deb $REPO-security ${OSVER}/updates main >> ${CHROOT}/etc/apt/sources.list
+	;;
+ubuntu)
+	echo deb $REPO $OSVER main universe > ${CHROOT}/etc/apt/sources.list
+	echo deb $REPO ${OSVER}-updates main universe >> ${CHROOT}/etc/apt/sources.list
+	echo deb $REPO ${OSVER}-security main universe >> ${CHROOT}/etc/apt/sources.list
+	;;
+esac
+
+cat << EOL | chroot $CHROOT
+apt-get purge -y udev
+apt-get update
+apt-get -fy install
+apt-get -y upgrade
+apt-get -y install --no-install-recommends lsb-release
+# dh_auto_test of mbedtls (faketime) depends on /dev/shm. https://bugs.debian.org/778462
+mkdir -p ~ /dev/shm
+mount tmpfs /dev/shm -t tmpfs
+
+date > /TIMESTAMP1
+git config --global user.email "script@example.com"
+git config --global user.name "build script"
+if [ -n "$http_proxy" ]; then
+	git config --global proxy.http $http_proxy
+	echo Acquire::http::Proxy \"$http_proxy\"\; > /etc/apt/apt.conf
+	export http_proxy=$http_proxy
+	export https_proxy=$https_proxy
+	export no_proxy=$no_proxy
+fi
+cd /tmp
+wget https://raw.githubusercontent.com/shadowsocks/shadowsocks-libev/master/scripts/build_deb.sh
+chmod 755 build_deb.sh
+./build_deb.sh
+date > /TIMESTAMP2
+./build_deb.sh kcp
+umount /dev/shm
+EOL
+
+TIMESTAMP1=$(cat ${CHROOT}/TIMESTAMP1)
+TIMESTAMP2=$(cat ${CHROOT}/TIMESTAMP2)
+TIMESTAMP3=$(date)
+
+printf \\n"All built deb packages:"\\n
+ls -l ${CHROOT}/tmp/*.deb
+echo
+echo Start-Time: $TIMESTAMP0
+echo ChrootDone: $TIMESTAMP1
+echo SsDeb-Done: $TIMESTAMP2
+echo \ Kcp-Done : $TIMESTAMP3