Add lftp package (#3987)

LFTP is a file transfer program that supports FTP, HTTP, SFTP, FISH, and
BitTorrent. It can act like rsync but over FTP.

Tested on ARM.

packages/lftp.rb

+require 'package'
+
+class Lftp < Package
+  description 'LFTP is a sophisticated file transfer program for ftp/http/sftp/fish/torrent'
+  homepage 'https://lftp.yar.ru'
+  version '4.9.1'
+  source_url 'https://lftp.yar.ru/ftp/lftp-4.9.1.tar.xz'
+  source_sha256 '5969fcaefd102955dd882f3bcd8962198bc537224749ed92f206f415207a024b'
+
+  binary_url ({
+  })
+  binary_sha256 ({
+  })
+
+
+  def self.build
+    system "./configure \
+      --prefix=#{CREW_PREFIX} \
+      --libdir=#{CREW_LIB_PREFIX} \
+      --disable-nls \
+      --with-linux-crypto"
+    system 'make'
+  end
+
+  def self.install
+    system 'make', "DESTDIR=#{CREW_DEST_DIR}", 'install'
+  end
+end