Update src/client/opamAction.ml

Co-authored-by: David Allsopp <[email protected]>

src/client/opamAction.ml

@@ -542,7 +542,12 @@ let compilation_env t opam =
                   git_location ~comment:"Git binary path"]) @
       let cygwin_env = match OpamStd.Env.getopt "CYGWIN" with
         | None | Some "" -> "winsymlinks:native"
-        | Some prev -> "winsymlinks:native " ^ prev
+        | Some prev ->
+          let is_native s = (s = "winsymlinks:nativestrict" || s = "winsymlinks:native") in
+          if List.exists is_native (String.split_on_char ' ' prev) then
+            prev (* Either winsymlinks:native or winsymlinks:nativestrict already in CYGWIN *)
+          else
+            prev ^ " winsymlinks:native" (* Override any other setting *)
       in
       [ OpamTypesBase.env_update_resolved "CYGWIN" Eq cygwin_env
           ~comment:"winsymlinks:native" ]