Makemessages --ignore option doesn't work for directories under Windows

[Ramiro Morales]

When running the i18n.test_extraction tests under Windows, the following failures happen:

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FAIL: test_ignore_subdirectory (i18n.test_extraction.IgnoredExtractorTests)
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Traceback (most recent call last):
  File "D:\ramiro\django\upstream\tests\i18n\test_extraction.py", line 387, in test_ignore_subdirectory
    self.assertTrue("ignoring directory subdir" in out)
AssertionError: False is not true

======================================================================
FAIL: test_media_static_dirs_ignored (i18n.test_extraction.IgnoredExtractorTests)
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Traceback (most recent call last):
  File "d:\ramiro\django\upstream\django\test\utils.py", line 281, in inner
    return test_func(*args, **kwargs)
  File "D:\ramiro\django\upstream\tests\i18n\test_extraction.py", line 402, in test_media_static_dirs_ignored
    self.assertIn("ignoring directory static_root", out)
AssertionError: u'ignoring directory static_root' not found in 'examining files with the extensions: .html and .txt\nprocessing file __init__.py in .\nprocessing file code.sample in .\nprocessing file ignored.html in .\\ignore_dir\nprocessing file ja
vascript.js in .\nprocessing file media_ignored.html in .\\media_root\nprocessing file not_utf8.sample in .\nprocessing file static_ignored.html in .\\static_root\nprocessing file comments.thtml in .\\templates\nprocessing file empty.html in .\\templ
ates\nprocessing file plural.djtpl in .\\templates\nprocessing file ignored.html in .\\templates\\subdir\nprocessing file template_with_error.tpl in .\\templates\nprocessing file test.html in .\\templates\nprocessing file xxx_ignored.html in .\\templ
ates\nprocessing locale de\ncopying plural forms: "Plural-Forms: nplurals=2; plural=(n != 1);\\n"\n'

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Ran 34 tests in 5.670s

FAILED (failures=2)

This is caused because code is trying to perform matching of dirs specs with a trailing '/*' but the path representation it uses at that point is in native format (using '\' path separators).

Refs #20422
Refs #22336

[Ramiro Morales]

PR: ​https://github.com/django/django/pull/3075