Huge number of temporary files when comparing src:wine artifacts

This bug was originally reported by Mattia Rizzolo (mattia@debian.org) in Debian bug #878342:

Package: diffoscope
Version 87
Severity: important

Today I tried to manually run diffoscope over a build of src:wine to see
whether we could get a usable diff.

Unfortunately, diffoscope died with ENSPC after 3 hours and half.  The
partition had ~50 GB free when I started diffoscope, and after it died
it left around 21 GB of temporary files, not sure whether all the 50 GB
were used in a specific moment, but even 21 GB are a lot.

I have the artifacts available (~ 200 MB) if anybody wants to
investigate.