Use opam pin-depends to use correct why3 version.

caisar.opam

@@ -19,7 +19,7 @@ depends: [
   "odoc" {with-doc}
 ]
 build: [
-  ["dune" "subst" "--root" "."] {dev}
+  ["dune" "subst"] {dev}
   [
     "dune"
     "build"
@@ -27,11 +27,13 @@ build: [
     name
     "-j"
     jobs
-    "--promote-install-files"
-    "false"
+    "--promote-install-files=false"
     "@install"
     "@runtest" {with-test}
     "@doc" {with-doc}
   ]
   ["dune" "install" "-p" name "--create-install-files" name]
 ]
+pin-depends: [
+  [ "why3" "git+https://gitlab.inria.fr/why3/why3.git#autodetection_from_file" ]
+]

caisar.opam.template

+pin-depends: [
+  [ "why3" "git+https://gitlab.inria.fr/why3/why3.git#autodetection_from_file" ]
+]