Dune installs empty META file for package with no library

[dra27]

If a package defines executables only, Dune generates a META file containing a blank line and installs it. cppo, since its conversion to Jbuilder in v1.6.0 has had this cppo.install generated:

lib: [
  "_build/install/default/lib/cppo/META"
  "_build/install/default/lib/cppo/dune-package"
  "_build/install/default/lib/cppo/opam"
]
bin: [
  "_build/install/default/bin/cppo"
]
doc: [
  "_build/install/default/doc/cppo/LICENSE.md"
  "_build/install/default/doc/cppo/README.md"
]

but because META is empty, you get this from ocamlfind list:

cppo                (version: n/a)
cppo_ocamlbuild     (version: 1.6.6)

Dune should either not generate a META file at all or should put at least a version field in it. If META is written, then I think a synopsis field might also be wanted for executable which would go in description in the META file.

I have no opinion on whether there should be a META file at all (prior to 1.6.0, cppo didn't have one, unsurprisingly).

We should indeed generate no META and no dune-package file

[dra27]

I agree - although note from the linked PR that that change is detectable, so it might want to be tied to a specific dune language version?

Indeed. Tying it to a specific dune language version seems good