Temp directory created by copy_images (which contains copies of .png files
from any given icon-themes folder) was left behind. Happening at least since
commit 4e3dc8c1

Date:   Fri Jun 3 17:09:14 2016 +0200

    remove use of Archive::Zip

With packimages.pl now used to package also screenshot images (in
multiple languages), tmp fills up quickly. This is fatal on Windows

Change-Id: Ie35c33277a80ed9085815f30b846bb97a365afb1
Reviewed-on: https://gerrit.libreoffice.org/31947Reviewed-by: Katarina Behrens <Katarina.Behrens@cib.de>
Tested-by: Katarina Behrens <Katarina.Behrens@cib.de>