title: Compile unison 2.48.4 build with OCaml version 4.08.1 on Manjaro
body: <p>I need a specific unison version compilied with a specific OCaml version to work together with the unison package on Ubuntu Server 20.04 LTS.
  I need unison 2.48.4 build with OCaml version 4.08.1. The package in AUR seems to be build with another OCaml version and cannot be used in my case.</p>
  <p>In the repositories of Manjaro only unison 2.52 and OCaml version 4.13.1 are available and currently installed on my system.</p>
  <p>Can somebody give me newbie-dummy guide how to install and build with specific versions of both programs? And where I get the source files from?</p>
  <p>Thank you very much.</p>