Also include the XScreenSaver libraries (confusingly named libXss) which are...

Also include the XScreenSaver libraries (confusingly named libXss) which are needed by Kaffeine as well.

Ref T10931
Status Job ID Name Coverage
  Build
manual #7515
docker allowed to fail manual
kdeorg/appimage-base
manual #7516
docker allowed to fail manual
kdeorg/staticweb