Admin/ocaml/opam/x86_64-cygwin/opam

more explicit opam dependencies;

#!/usr/bin/env bash

if [ -e /usr/bin/opam ]; then
  exec /usr/bin/opam "$@"
else
  echo >&2 "Missing opam executable: please install Cygwin package \"opam\" version 2.0.x"
  exit 2
fi