bitbake: doc: Makefile: turn warnings into errors by default

-W is for turning warnings into errors, --keep-going to make sure the
whole documentation is built and all warnings will be printed before
failing.

Since there's currently no warning, it's time to introduce it!

(Bitbake rev: 6b0b3d707f662ca7b1d0de99fe032e4f35867d10)

Signed-off-by: Quentin Schulz <quentin.schulz@theobroma-systems.com>
Signed-off-by: Quentin Schulz <foss@0leil.net>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/doc/Makefile

@@ -3,7 +3,7 @@
 
 # You can set these variables from the command line, and also
 # from the environment for the first two.
-SPHINXOPTS    ?= -j auto
+SPHINXOPTS    ?= -W --keep-going -j auto
 SPHINXBUILD   ?= sphinx-build
 SOURCEDIR     = .
 BUILDDIR      = _build