Gracefully deal with jars containing .clj and .cljc for same namespace

[martinklepsch]

Instaparse 1.4.9 contains one .clj and one .cljc file for each namespace for backwards compatibility. This is done via cljsee which transforms .cljc to plain .clj files before packaging.

instaparse/abnf.clj
instaparse/abnf.cljc
instaparse/auto_flatten_seq.clj
instaparse/auto_flatten_seq.cljc
instaparse/cfg.clj
instaparse/cfg.cljc

Now we use clojure.tools.namespace.find/find-sources-in-dir to find namespaces in a directory and it will return duplicates in this situation resulting in a weird analysis result with some namespaces duplicated, eventually failing because we have a database constraint not to insert two namespaces with the same name for the same artifact/platform.

Probably all that's needed is wrapping the call in a (set ,,,).