Path troubles when using SPHINXDIRS option

[Mauro Carvalho Chehab <mchehab+huawei@kernel.org>]

Hi,

While building from v5.7-rc2 + media, I noticed that SPHINXDIRS option
stopped working.

What happens is that, if we don't pass this option, Sphinx assumes that
the "absolute" path is "Documentation/". So, include options like this:

	.. include:: /ABI/stable/firewire-cdev
	    :literal:


would be evaluated as Documentation/ABI/stable/firewire-cdev if built
without SPHINXDIRS. However, if we do SPHINXDIRS=driver-api, then
the "absolute" patch would be "Documentation/driver-api", causing this
error:

	Sphinx parallel build error:
	docutils.utils.SystemMessage: /devel/v4l/patchwork/Documentation/driver-api/firewire.rst:22: (SEVERE/4) Problems with "include" directive path:

This is specially bad for build jobs (like one we have on jenkins that
is meant to test media patches), as, due to some Sphinx bug, prevents
sphinx-build to stop, making the toolset to run forever.

I suspect that some change at conf.py could address the path issue.

I'll try to investigate further.

Just to be 100% sure that this is not some version-specific bad
behavior, I tested (using the latest patch version) Sphinx from
version 1.7.9 up to 2.4.4. The same two errors happen on all
versions.

Markus,

Maybe you may have some idea about how to fix those issues.

The parallel build error would likely require fixing something
inside Sphinx code, making it abort if it gets a "SEVERE" error.

Regards,
Mauro