add ocaml as dependency to rtree packages

Author: haochenx

packages/rtree/rtree.0.1.0/opam

@@ -9,6 +9,7 @@ tags: ["spatial" "index"]
 homepage: "https://github.com/geocaml/ocaml-rtree"
 bug-reports: "https://github.com/geocaml/ocaml-rtree/issues"
 depends: [
+  "ocaml"
   "dune" {>= "3.6"}
   "repr" {>= "0.4.0"}
   "bechamel" {with-test}

packages/rtree/rtree.0.1.1/opam

@@ -9,6 +9,7 @@ tags: ["spatial" "index"]
 homepage: "https://github.com/geocaml/ocaml-rtree"
 bug-reports: "https://github.com/geocaml/ocaml-rtree/issues"
 depends: [
+  "ocaml"
   "dune" {>= "3.6"}
   "repr" {>= "0.4.0"}
   "bechamel" {with-test}