'dromedary.py' misses data for 'unix'

[shayne-fletcher]

the prebuilt_ocaml_library definition of the OCaml API 'unix' library generated by 'dromedary.py' misses native and bytecode C library data.

what 'domedary.py' generates is

prebuilt_ocaml_library(
    name = "unix",
    ...
    native_c_libs = [],
    bytecode_c_libs = [],
    ...
    )

and what 'dromedary.py' should generate is

prebuilt_ocaml_library(
    name = "unix",
    ...
    native_c_libs = [
        "opam/lib/ocaml/libunixnat.a"
    ],
    bytecode_c_libs = [
        "opam/lib/ocaml/libunixbyt.a"
    ],
    ...
    )

this means OCaml binaries that use the Unix module fail to link.

example link failures can be seen on the test-unix-workflow branch of this ocaml-scripts clone by executing test-unix.yml. see these build logs.

the workflow attempts to build the target root//test:test-unix, a program that calls the Unix.getlogin function.

[shayne-fletcher]

this commit 0e81cfd looks like a good starting point (cc @EmeraldShift ). current ocaml version is 5.1.1.