Expected Behavior

Successful compilation using the pkg-config instructions in the dune quickstart.
Relevant quickstart section: https://dune.readthedocs.io/en/stable/quick-start.html#defining-a-library-with-c-stubs-using-pkg-config

Actual Behavior

Using the instructions that show this rule for discover:

(action  (run %{discover} -ocamlc %{ocamlc})))

I get this error:

$ dune build examples/simple.exe                                                                                                                      Mon Apr 20 13:10:30 2020
    discover lib/c_flags.sexp,lib/c_library_flags.sexp (exit 2)
(cd _build/default/lib && config/discover.exe -ocamlc /Users/tbrady/.opam/4.09.0/bin/ocamlc.opt)
config/discover.exe: unknown option '-ocamlc'.
discover.exe [OPTIONS]
  -verbose      be verbose
  -dest-dir DIR save temporary files to this directory
  -help         Display this list of options
  --help        Display this list of options

Reproduction

1. Visit this branch in my repo: https://github.com/travisbrady/ocaml-vw/tree/todune
2. Run $ dune build examples/simple.exe
3. View error shown above

Specifications

• Version of dune (output of dune --version): 2.5.0
• Version of ocaml (output of ocamlc --version): 4.09.0
• Operating system (distribution and version): Darwin AUSC02QRF6FG8WP 19.3.0 Darwin Kernel Version 19.3.0: Thu Jan 9 20:58:23 PST 2020; root:xnu-6153.81.5~1/RELEASE_X86_64 x86_64

Additional information

• Link to gist with verbose output (run dune with the --verbose flag): https://gist.github.com/travisbrady/a2b5449010941a4509a4c64feec96a40