[Debian-pan-maintainers] Bug#1071132: ovito accesses the internet during the build

[Drew Parsons]

Package: ovito
Followup-For: Bug #1071132

For the record, the problem is the sphinx flag -W,
which treats warnings as errors.

This flag is activated by default by ovito's cmake configuration option
OVITO_BUILD_DOCUMENTATION_STRICT.
Our build will be more robust against doc build issues if we switch it
off.