Since resolution of bug #923433, dcmtk is now built with the
convinient charls copy. It would make sense in the long term to switch
to the system charls (debian package).

This has been accepted as feature by upstream:

* https://support.dcmtk.org/redmine/issues/344#note-5

<quote>
The implementation strategy for DCMTK decided by the team will be to
keep the internal CharLS version available in DCMTK (for platforms
where CharLS is not available as an external library or compilers that
do not support C++11/C++14) but provide an option to compile DCMTK
either with the internal or with an external CharLS library. For the
external CharLS library, we will primarily aim at supporting CharLS
2.x. This does require several modification of the build system,
though, and these will only be implemented after DCMTK 3.6.5.
</quote>

Control: tags -1 + wontfix

I had a quick lookup at upstream tracker: there seem to be no
plans anymore[1] to bring the necessary changes.  I tag the
issue wontfix for now.  I don't close it yet, because there is
still the option to attune the build system ourselves.  But,
that is not something I'm feeling confident to do myself.

[1]: https://support.dcmtk.org/redmine/issues/344#note-6