Restrict binaryen_dsl

Upstream fix: vincentdchan/ocaml-binaryen-dsl#1

Author: emillon

packages/binaryen_dsl/binaryen_dsl.0.7/opam

@@ -15,7 +15,7 @@ depends: [
   "ocaml"
   "core" {< "v0.15"}
   "dune" {>= "2.8"}
-  "ctypes" {>= "0.14.0"}
+  "ctypes" {>= "0.14.0" & < "0.21.0"}
   "libbinaryen" {< "102"}
 ]
 build: [