Do not generate context names in a clever way

Now, we always require local siwtchse to set the name.

Signed-off-by: Rudi Grinberg <me@rgrinberg.com>

src/dune/workspace.ml

@@ -189,7 +189,7 @@ module Context = struct
         match name with
         | Some s -> s
         | None -> (
-          let name = Filename.basename switch ^ Common.fdo_suffix base in
+          let name = switch ^ Common.fdo_suffix base in
           match Context_name.of_string_opt name with
           | Some s -> s
           | None ->