Add ck4up package (#3645)

Ck4up is a small command-line utility primarily intended for CRUX ports
maintainers to watch http and ftp sites for updates, but may also be useful for
others.

Tested on ARM.

packages/ck4up.rb

+require 'package'
+
+class Ck4up < Package
+  description 'Check for Updates, a utility to monitor web pages for updates'
+  homepage 'http://jue.li/crux/ck4up'
+  version '1.4'
+  source_url 'http://jue.li/crux/ck4up/ck4up-1.4.tar.gz'
+  source_sha256 '37f2f981cfdb6811a906e5520cb27203cb5ecb725d2180aaac59d377c1ac9fbf'
+
+  binary_url ({
+  })
+  binary_sha256 ({
+  })
+
+  def self.build
+  end
+
+  def self.install
+    system 'make', "PREFIX=#{CREW_PREFIX}", "DESTDIR=#{CREW_DEST_DIR}", 'install'
+  end
+
+  def self.postinstall
+    puts
+    puts "A configuration file is required to use ck4up.".lightblue
+    puts "By default it looks for ~/.ck4up/ck4up.conf".lightblue
+    puts
+  end
+end