Test failure under WASI due to assuming ctypes is always available

[brettcannon]

________________ test_glibc_version_string_ctypes_raise_oserror ________________

monkeypatch = <_pytest.monkeypatch.MonkeyPatch object at 0x21a84b0>

    def test_glibc_version_string_ctypes_raise_oserror(monkeypatch):
        def patched_cdll(name):
            raise OSError("Dynamic loading not supported")

>       monkeypatch.setattr(ctypes, "CDLL", patched_cdll)
E       AttributeError: None has no attribute 'CDLL'

tests/test_manylinux.py:146: AttributeError

packaging/tests/test_manylinux.py

Lines 142 to 147 in 1b9da44

	def test_glibc_version_string_ctypes_raise_oserror(monkeypatch):
	def patched_cdll(name):
	raise OSError("Dynamic loading not supported")
	monkeypatch.setattr(ctypes, "CDLL", patched_cdll)
	assert _glibc_version_string_ctypes() is None

[brettcannon]

Should just require an appropriate skipIf decorator.

[kevinchang96]

Hi @brettcannon, I'd like to work on this issue. Can you please assign it to me?

[brettcannon]

@kevinchang96 feel free to go ahead and submit a PR; I personally prefer not assigning issues to non-maintainers.