The patch will make it build when building it with ocaml-ppxlib@0.23.0.
* gnu/packages/patches/ocaml-ppx-variants-ppxlib-api-change.patch: New file.
* gnu/local.mk (dist_patch_DATA): Register it.
* gnu/packages/ocaml.scm (ocaml-ppx-variants-conv): Apply the patch.
Signed-off-by: Ludovic Courtès <ludo@gnu.org>
