Consider managing source/target options in :javac-options

Some Clojure projects define -source and -target in the :javac-options key. The values may not be in sync with the compatibility levels supported in Debian, leading to FTBFS issues like the one reported in this merge request on the cheshire-clojure package.

It might also be worthwhile to manage this by default for all Clojure packages, by setting the minimum -source and -target options (sourced from java-common). This might help avoid issues such as #1031260 when a user attempts to use an older JVM package with newer Clojure libraries.