Support `:foreign-libs` without `:file` to allow use of `:global-exports` already provided by the webpage

Question

It would be useful to be able to use `:foreign-libs` even when a library is already globally available on a page.
<script src="https://apis.google.com/js/platform.js"></script>

{:foreign-libs
 [{:provides ["google.api"]
   :global-exports {google.api gapi}}]}

Answer 1

Reference: https://clojure.atlassian.net/browse/CLJS-2810 (reported by alex+import)