Utilities/Sphinx: Print path to index.html in build output

Print the url to index.html in the build output, just so one can
"open in browser" from the context menu in some terminals.

Utilities/Sphinx/CMakeLists.txt

@@ -58,6 +58,13 @@ configure_file(conf.py.in conf.py @ONLY)
 set(doc_formats "")
 if(SPHINX_HTML)
   list(APPEND doc_formats html)
+
+  # we provide the path to the produced html output in the console
+  # for tools that support URI protocol schemes
+  set(html_extra_commands
+    COMMAND ${CMAKE_COMMAND} -E echo "sphinx-build html: HTML documentation generated in file://${CMAKE_CURRENT_BINARY_DIR}/html/index.html"
+  )
+
 endif()
 if(SPHINX_MAN)
   list(APPEND doc_formats man)