In certain conditions the parallel calls to sphinx-build could
collide, yielding a crash like
Exception occurred:
File "/usr/lib/python3/dist-packages/sphinx/environment.py", line 1261, in get_doctree
doctree = pickle.load(f)
EOFError: Ran out of input
%.gz: %
rm -f $@ && gzip --stdout $^ > $@
+# Sequentialize the calls to sphinx-build to avoid races with
+# reading/writing cached state. This uses GNU make specific
+# "order-only" prerequisites.
+
+sphinx-html: | $(DOCBUILDDIR)/.roff.stamp
+sphinx-texinfo: | sphinx-html
+sphinx-info: | sphinx-texinfo
+
sphinx-html:
$(SPHINXBUILD) -b html $(ALLSPHINXOPTS) $(DOCBUILDDIR)/html