I don't think you will get a definitive answer on this list.   Here is a thought experiment showing why.  Suppose J. Random Hacker decides to write a compiler from WhizBangLang to OCaml byte code.  Under the assumption that OCaml developers are not omniscient, the way they would learn about J. Random Hacker's efforts is if s/he either: a) announces the new language in some venue that OCaml developers watch or b) finds [what s/he believes are] bugs in the OCaml byte code interpreter and files bug reports against it.  It isn't clear to me that our J Random Hacker must needs do either of those things.

The ocamlrun program, shipped with the OCaml distribution and documented at http://caml.inria.fr/pub/docs/manual-ocaml/runtime.html is the standard interpreter for the OCaml byte code. 

For the OCaml compiler, the byte code is a target (as opposed to a source or an intermediate representation), so the existing OCaml tool chain does not support compiling byte code, to the best of my knowledge (AFAIK projects like Bucklescript and js_of_ocaml use the OCaml front-end and intermediate representation, but supply a different compiler back end).

I think that question is answered in the documentation of ocamlrun.   You probably will also want to peruse http://caml.inria.fr/pub/docs/manual-ocaml/intfc.html and specifically the discussion of static and dynamic linking of C code with OCaml code.

 

I am not entirely certain what the intended antecedent of "this" is here.  If "this" is "a compiler that targets OCaml byte code", then please see my answer above.  If you feel that the current design of "ocamlrun for standard primitives + the '-custom' flag to the OCaml compiler for non-standard primitives" is failing to address a need, then a description of the need that isn't being addressed would be a good starting point for discussion. ;-)

Hope this helps

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Best,

Zhenya