doc: automake: Add support for sphinx 4.0.

File layout for man pages in sphinx 4 by default changed [1] from:

  Documentation/_ref/man/page.section

To:

  Documentation/_ref/man/section/page.section

Ajusting our build scripts so they will be able to locate files
in new places.  This fixes our CI build.

[1] sphinx-doc/sphinx#7996

Signed-off-by: Ilya Maximets <i.maximets@ovn.org>

Documentation/automake.mk

@@ -216,8 +216,13 @@ install-man-rst: docs-check
 	    $(extract_stem_and_section); \
 	    echo " $(MKDIR_P) '$(DESTDIR)'\"$$mandir\""; \
 	    $(MKDIR_P) '$(DESTDIR)'"$$mandir"; \
-	    echo " $(INSTALL_DATA) $(SPHINXBUILDDIR)/man/$$stem.$$section '$(DESTDIR)'\"$$mandir/$$stem.$$section\""; \
-	    $(INSTALL_DATA) $(SPHINXBUILDDIR)/man/$$stem.$$section '$(DESTDIR)'"$$mandir/$$stem.$$section"; \
+	    if -f $(SPHINXBUILDDIR)/man/$$stem.$$section; then
+	        filepath=$(SPHINXBUILDDIR)/man/$$stem.$$section
+	    else
+	        filepath=$(SPHINXBUILDDIR)/man/$$section/$$stem.$$section
+	    fi
+	    echo " $(INSTALL_DATA) $(filepath) '$(DESTDIR)'\"$$mandir/$$stem.$$section\""; \
+	    $(INSTALL_DATA) $(filepath) '$(DESTDIR)'"$$mandir/$$stem.$$section"; \
 	done
 else
 install-man-rst: