Support managing project of ocaml edition A from drom of ocaml edition B

[glyh]

I got this error when I attempted:

$ drom build
drom: Entering directory '/home/lyh/Documents/CS/PL/honu_mac'
Warning: drom is not correctly configured, no share_dir found
   * ocamlup share/drom points to directory with missing "/home/lyh/.ocamlup/share/drom/skeletons"
   * OPAM_SWITCH_PREFIX points to directory with missing "/home/lyh/Documents/CS/PL/honu_mac/_opam/share/drom/skeletons"
Warning: could not load licenses from share/drom/licenses
Warning: could not load skeletons from share/drom/skeletons/package
Warning: could not load skeletons from share/drom/skeletons/project
Error: Missing skeleton "program"

It's clear that drom is mismatched. However I can't install drom inside this swith, as the following reason:

$ opam install drom
[ERROR] Package conflict!
  * No agreement on the version of ocaml:
    - (invariant) → ocaml = 5.1.0
    - drom → drom_lib < 0.3.0 → ez_config < 1.0.0 → dune < 3.0.0 → ocaml < 4.08.0
    You can temporarily relax the switch invariant with `--update-invariant'

No solution found, exiting

Solution would be either dropping ez_config, or separate the 2 relation.

[struktured]

@glyh I tried doing the admittedly awkward opam exec --switch=your-drom-env drom but I doubt that's a reliable approach.

[lefessan]

Indeed, ez_config is there, but not used at all...

[lefessan]

Note that I would advise not to use the opam version, but install it outside of opam trees, as drom has no dependency inside its switch (current version is supposed to checkout drom-share using git)

[glyh]

@lefessan that's exactly what I tried, but drom doesn't seem to be able to manage that.