Linkcheck marks local links broken when they reference files produced later, during in HTML building

[tuukkamustonen]

Describe the bug

After #5208 sphinx-build -b linkcheck is now checking links to local files, too. That was released in Sphinx 3.2.0.

However, it generates false positives in certain cases.

To Reproduce

As in:

.. figure:: architecture.png
   :target: ../_images/architecture.png

Target (../_images/architecture.png) exists and works correctly in the rendered HTML, but link checker marks it as failure.

@tk0miya commented at #5208 (comment):

The target file will be available only on building HTML. Because the files under _images are copied by HTML builder. It means they're not available on linkcheck. It's like a chicken-and-egg problem.

Expected behavior

Sphinx should not mark the link as broken.

Environment info

• OS: Linux
• Python version: 3.7.10
• Sphinx version: 3.5.4
• Sphinx extensions: n/a
• Extra tools: n/a

[staticdev]

@tk0miya I tried to give my first contribution to sphinx on this issue. I was able to debug and understand the problem. But the solution is not clear to me because of your comment of chicken-egg problem. What is the impact of changing the order to run linkcheck AFTER the build files are generated?