Flex path to doxygen data with glob

doc/Makefile

@@ -176,11 +176,11 @@ doctest:
 	@echo "Testing of doctests in the sources finished, look at the " \
 	      "results in $(BUILDDIR)/doctest/output.txt."
 
-coverage: doxygen/xml
-	mkdir -p $(BUILDDIR)
-	python3 -m coverxygen --xml-dir doxygen/xml --src-dir .. --format json-summary --output $(BUILDDIR)/doc-coverage.json
-	@echo "Testing of coverage in the sources finished, look at the " \
-	      "results in $(BUILDDIR)/doc-coverage.json."
+coverage:
+    mkdir -p $(BUILDDIR)
+    python3 -m coverxygen --xml-dir doxy*/xml --src-dir .. --format json-summary --output $(BUILDDIR)/doc-coverage.json
+    @echo "Testing of coverage in the sources finished, look at the " \
+              "results in $(BUILDDIR)/doc-coverage.json."
 
 xml:
 	$(SPHINXBUILD) -b xml $(ALLSPHINXOPTS) $(BUILDDIR)/xml
@@ -197,6 +197,3 @@ pseudoxml:
 clean:
 	rm -rf doxygen/ api/
 	@$(SPHINXBUILD) -M clean "$(SOURCEDIR)" "$(BUILDDIR)" $(SPHINXOPTS) $(O)
-
-doxygen/xml:
-	cd .. && doxygen