Add scron package

packages/scron.rb

+require 'package'
+
+class Scron < Package
+  description 'Simple cron daemon.'
+  homepage 'https://git.2f30.org/scron/'
+  version '0.4'
+  source_url 'https://git.2f30.org/scron/log.html'
+  source_sha256 'e37c93d910cc5e0793a6d354d5a3de6f1e963656e7546abb7bca5410c90792df'
+
+  binary_url ({
+  })
+  binary_sha256 ({
+  })
+
+  def self.build
+    system 'git clone git://git.2f30.org/scron.git'
+    Dir.chdir 'scron' do
+      system 'git checkout 0.4'
+      system "sed -i 's,PREFIX = /usr/local,PREFIX = #{CREW_DEST_PREFIX},' Makefile"
+      system 'make'
+    end
+  end
+
+  def self.install
+    Dir.chdir 'scron' do
+      system 'make install'
+    end
+  end
+end