Bug#875688: libreoffice-report-builder: report builder inactive in 5.4

[Lionel Elie Mamane <lionel@mamane.lu>]

retitle 875688 report builder inactive; only legacy reports can be created and run
thanks

For clarity, there are two reporting systems in LibreOffice:

1) Report Design (entirely in C++), the "old legacy one".

2) Report Builder, which used to be an extension, then was a bundled
   extension, and then became an optional but integrated part of
   LibreOffice (installed by default, but optional).

The Debian package of 5.4 behaves as if the optional part of
LibreOffice "Report Builder" was not installed, although the packages
libreoffice-report-builder and libreoffice-report-builder-bin are
installed. I haven't diagnosed why.

The immediate cause is that in file
 dbaccess/source/ui/misc/linkeddocuments.cxx
 function OLinkedDocumentsAccess::open, the call to impl_open throws a
 css::io::WrongFormatException,
but what is the underlying reason for that? Probably the internal
LibreOffice registry doesn't have properly registered the optional
"Report Builder" part (could be an error in
/usr/lib/libreoffice/share/registry/reportbuilder.xcd or that file is
not loaded), or it fails to load for some reason.