Update dune dependency version to 3.8 and add conflicts

Author: jim-portegies

packages/coq-waterproof/coq-waterproof.3.0.0+8.20/opam

@@ -24,7 +24,7 @@ bug-reports: "https://github.com/impermeable/coq-waterproof/issues"
 depends: [
   "ocaml" {>= "4.09.0"}
   "coq" {>= "8.20" & < "8.21" | = "dev"}
-  "dune" {>= "3.6"}
+  "dune" {>= "3.8"}
 ]
 
 build: [
@@ -33,6 +33,8 @@ build: [
 
 available: (arch != "s390x") & (arch != "ppc64") & (os != "win32")
 
+conflicts: [ "ocaml-option-bytecode-only" ]
+
 tags: [
   "keyword:mathematics education"
   "category:Mathematics/Education"