Adds logging in two branches that was missing from the logger.debug. Gives output like:

[build target] outdated 'auto_examples/future/plot_future_imports' from dependency '/home/larsoner/python/sphinx-gallery/sphinx_gallery/tests/tinybuild/doc/auto_examples/future/images/thumb/sphx_glr_plot_future_imports_broken_thumb.png': 2023-08-09 18:36:25.911416 -> 2023-08-09 18:36:34.238679

Perhaps it's a bit verbose but it at least indicates that this file is marked outdated because a dependency of it was created after the file that uses it.

BUT this brings up an issue -- the dependency itself was not changed the two calls to make html. The conditional if depmtime > mtime: around line 501 checks if the mtime of the file during previous build is older than that of the dependency in this build, when it seems like it should check if the mtime of the dependency during previous build is older than that of the dependency in this build. In other words, if I create index.rst, then create whatever.inc, and .. include: whatever.inc, index.rst will always show up as out of date just because of the order in which I created index and whatever.inc.

Should I try to fix that here as well? It seems like a potentially tough thing to fix because it would mean adding all dependency files to self.all_docs (where self is the BuildEnvironment) -- or maybe better adding a self.all_deps that is a str->float mtime mapping for all dependencies.