Here is two patches for libreoffice, both are changes of the configure flags
in the definition.

First is a change according to a comment. I started looking at these because
I wanted to check digital signatures and NSS was needed. Not sure NPAPI is
needed for NSS, but it is now enabled as per the old comment.

Second is enabling gtk2. This fixes  bug#30642 for me. I think this is
because I'm not using gnome and therefore libreoffice can't find what it
needs. But Idk.

Filechooser dialog and digital signatures work with these 2 changes here.