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?

(alias
 (name default)
 (deps phoebe.bc)
)

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

(menhir
 (modules grammar)
)
  
(ocamllex lex)

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