Add unshield package

packages/unshield.rb

+require 'package'
+
+class Unshield < Package
+  description 'Tool and library to extract CAB files from InstallShield installers.'
+  homepage 'https://github.com/twogood/unshield'
+  version '1.4.2'
+  source_url 'https://github.com/twogood/unshield/archive/1.4.2.tar.gz'
+  source_sha1 '02935c888b04507f0a14036773539a4f8c20a152'
+
+  depends_on 'cmake'
+
+  def self.build
+    system 'cmake .'
+    system 'make'
+  end
+
+  def self.install
+    system "mkdir -p #{CREW_DEST_DIR}/usr/local/man/man1"
+    system "cp man/* #{CREW_DEST_DIR}/usr/local/man/man1"
+    system "make", "DESTDIR=#{CREW_DEST_DIR}", "install"
+  end
+end