What Dune stanzas will create a .cmo?

I’m trying to debug a compiler I’ve written. To help with debugging, I’ve written print functions for some of its internal datatypes, and put them in a file called ‘print.ml’. I want to load them into ocamldebug with load_printer, but I don’t know how to create the .cmo containing the print functions.

This is what my Dune file looks like now. What stanzas do I need to add, to create the print.cmo?

 (name default)
 (deps phoebe.bc)

 (name phoebe)
 (libraries unix)
 (modules utility error ast symbol verilog parse grammar lex phoebe)
 (modes (byte exe))

 (modules grammar)
(ocamllex lex)

 (section bin)
 (files (phoebe.bc as phoebe))