OXT-1253: ocaml: Align with layer refactorisation.

[eric-ch]

This is now defined in meta-openxt-ocaml-layer under the findlib.bbclass and ocaml.bbclass.

This was forgotten in the original set of PRs and is no longer required.

[eric-ch]

Building #1272

[dpsmith]

Yeah! +1! Glad to see more of this common config getting moved out of local.conf where it doesn't belong.

[eric-ch]

I forgot some of it, now requires:

• https://github.com/OpenXT/meta-openxt-ocaml-platform/pull/7
• https://github.com/OpenXT/xenclient-oe/pull/814

Building #1274

[jean-edouard]

LGTM, merging all PRs tomorrow morning.