Speedup: build docs in parallel (GH-92733) (GH-92850)

(cherry picked from commit a487623)

Author: hugovk

.github/workflows/doc.yml

@@ -37,7 +37,7 @@ jobs:
     - name: 'Install build dependencies'
       run: make -C Doc/ PYTHON=../python venv
     - name: 'Build documentation'
-      run: xvfb-run make -C Doc/ PYTHON=../python SPHINXOPTS="-q -W --keep-going -j4" doctest html suspicious
+      run: xvfb-run make -C Doc/ PYTHON=../python SPHINXOPTS="-q -W --keep-going" doctest html suspicious
     - name: 'Upload'
       uses: actions/upload-artifact@v3
       with:

Doc/Makefile

@@ -17,7 +17,7 @@ SPHINXERRORHANDLING = -W
 PAPEROPT_a4     = -D latex_elements.papersize=a4paper
 PAPEROPT_letter = -D latex_elements.papersize=letterpaper
 
-ALLSPHINXOPTS = -b $(BUILDER) -d build/doctrees $(PAPEROPT_$(PAPER)) \
+ALLSPHINXOPTS = -b $(BUILDER) -d build/doctrees $(PAPEROPT_$(PAPER)) -j auto \
                 $(SPHINXOPTS) $(SPHINXERRORHANDLING) . build/$(BUILDER) $(SOURCES)
 
 .PHONY: help build html htmlhelp latex text texinfo changes linkcheck \