gnu: ocaml-4.07: Ensure build with ocaml4.7-dune.

gnu: ocaml-4.07: Ensure build with ocaml4.7-dune.

* gnu/packages/ocaml.scm (ocaml4.07-gen, ocaml4.07-sedlex)
(ocaml4.07-ezjsonm, ocaml4.07-uri, ocaml4.07-charinfo-width)
(ocaml4.07-zed, ocaml4.07-lambda-term, ocaml4.07-utop)
(ocaml4.07-ppx-inline-test, ocaml4.07-earley, ocaml4.07-merlin)
(ocaml4.07-sexplib0, ocaml4.07-parsexp, ocaml4.07-sexplib)
(ocaml4.07-base, ocaml4.07-stdio, ocaml4.07-ppxlib, ocaml4.07-ppx-compare)
(ocaml4.07-fieldslib, ocaml4.07-variantslib, ocaml4.07-ppx-fields-conv)
(ocaml4.07-ppx-sexp-conv, ocaml4.07-ppx-variants-conv)
(ocaml4.07-ppx-custom-printf, ocaml4.07-bin-prot, ocaml4.07-ppx-hash)
(ocaml4.07-ppx-enumerate, ocaml4.07-ppx-bench, ocaml4.07-ppx-here)
(ocaml4.07-ppx-typerep, ocaml4.07-ppx-sexp-value, ocaml4.07-ppx-sexp-message)
(ocaml4.07-ppx-pipebang, ocaml4.07-ppx-optional, ocaml4.07-ppx-optcomp)
(ocaml4.07-ppx-let, ocaml4.07-ppx-fail, ocaml4.07-ppx-assert)
(ocaml4.07-ppx-expect, ocaml4.07-ppx-js-style, ocaml4.07-ppx-typerep-conv)
(ocaml4.07-ppx-base, ocaml4.07-ppx-bin-prot, ocaml4.07-ppx-jane)
(ocaml4.07-splittable-random, ocaml4.07-configurator, ocaml4.07-spawn)
(ocaml4.07-core, ocaml4.07-core-kernel)[arguments]: Use ocaml4.07-dune.