docs/sphinx: add static files to generated depfile

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>

docs/sphinx/depfile.py

@@ -13,6 +13,7 @@
 import os
 import sphinx
 import sys
+from pathlib import Path
 
 __version__ = '1.0'
 
@@ -25,6 +26,10 @@ def get_infiles(env):
         if hasattr(mod, '__file__'):
             if mod.__file__:
                 yield mod.__file__
+    # this is perhaps going to include unused files:
+    for static_path in env.config.html_static_path:
+        for path in Path(static_path).rglob('*'):
+            yield str(path)
 
 
 def write_depfile(app, exception):