ocaml-calendar 3.0.0 (in Fedora 39+ and briefly in RHEL 10) requires
ocaml-re, which we removed from RHEL 10, so now that package cannot
build. We don't need ocaml-calendar 3, version 2.04 will do fine.
Revert back to it.
Unfortunately to do this I had to introduce an epoch to get this to
override previous versions from RHEL 10.
I also had to remove debuginfo because that fails for unclear reasons.
I also had to do some porting for OCaml 5.
Richard W.M. Jones