There is an updated pull request by leahneukirchen against master on the void-packages repository

https://github.com/leahneukirchen/void-packages ocaml408
https://github.com/void-linux/void-packages/pull/12451

[WIP] OCaml 4.08
Missing/broken:
- [ ] ELFv2 patches for ppc64 (@q66)
- [ ] verifast
- [ ] coq
- [ ] mldonkey
- [ ] wyrd
- [ ] ocaml-lablgtk2
- [ ] unison
- [ ] pfff
- [ ] coccinelle
- [ ] camlp5
- [ ] camlp4
- [ ] opam

A patch file from https://github.com/void-linux/void-packages/pull/12451.patch is attached