updated command + alternative

Author: Ladislav Chvastaš

tox.ini

@@ -130,10 +130,14 @@ deps =
     -r{toxinidir}/doc/en/requirements.txt
     sphinx>=8.1.3
 commands =
-    sphinx-build -W -q --keep-going -b linkcheck . _build
+    sphinx-build -W -q --keep-going -b linkcheck -j auto . _build
+;    /bin/sh -c "sphinx-build -W -q --keep-going -b linkcheck -j auto . _build > linkcheck_output.txt 2>&1"
+
 setenv =
     # Sphinx is not clean of this warning.
     PYTHONWARNDEFAULTENCODING=
+;allowlist_externals =
+;    /bin/sh
 
 [testenv:regen]
 description =