Add pdftk package (#5825)

packages/pdftk.rb

+require 'package'
+
+class Pdftk < Package
+  description 'PDFtk is a simple tool for doing everyday things with PDF documents.'
+  homepage 'https://www.pdflabs.com/tools/pdftk-the-pdf-toolkit/'
+  version '3.2.2'
+  license 'GPL-2'
+  compatibility 'all'
+  source_url 'https://gitlab.com/pdftk-java/pdftk/-/archive/v3.2.2/pdftk-v3.2.2.tar.bz2'
+  source_sha256 'b315f1267947af337c0d1e8253fba26108eed6392b43633fe967093f42ad45eb'
+
+  depends_on 'jdk8'
+  depends_on 'gradle' => :build
+
+  def self.build
+    @pdftk = <<~EOF
+      #!/bin/bash
+      cd #{CREW_PREFIX}/share/pdftk
+      java -jar pdftk-all.jar "$@"
+    EOF
+    File.write('pdftk.sh', @pdftk)
+    system "JAVA_HOME=#{CREW_PREFIX} gradle shadowJar"
+  end
+
+  def self.install
+    FileUtils.mkdir_p "#{CREW_DEST_PREFIX}/bin"
+    FileUtils.mkdir_p "#{CREW_DEST_PREFIX}/share/pdftk"
+    FileUtils.mv 'build/libs/pdftk-all.jar', "#{CREW_DEST_PREFIX}/share/pdftk"
+    FileUtils.install 'pdftk.sh', "#{CREW_DEST_PREFIX}/bin/pdftk", mode: 0o755
+  end
+
+  def self.postinstall
+    puts "\nType 'pdftk' to get started.\n".lightblue
+  end
+end