hello I got the following in my dev.edn :duct.server/figwheel {} which results in :

:duct.server/figwheel {:css-dirs ["resources" "dev/resources"],
                        :builds [{:id "dev",
                                  :figwheel true,
                                  :source-paths ["dev/src" "src"],
                                  :build-options {:main firds-mirror4.client,
                                                  :output-to "/Users/.../public/js/main.js",
                                                  :output-dir "/Users/.../public/js",
                                                  :asset-path "/js",
                                                  :closure-defines {goog.DEBUG true},
                                                  :verbose false,
                                                  :preloads [devtools.preload],
                                                  :optimizations :none}}]},

Now, I'd like to add something to the :build-options

namely:

{:builds  [ {:id "dev"

                                          :build-options
                                              {:foreign-libs ^:replace [{:file "foreign_libs/codemirror_grammar.js" :provides ["cmg"]}]}}]}

but rather than merging it overrides the config.

What is the correct way to merge additional build option?