gh-120965: Skip test_zoneinfo.ExtensionBuiltTest if C extension is not available (#131104)

Co-authored-by: Paul Ganssle <1377457+pganssle@users.noreply.github.com>

Author: StanFromIreland

Lib/test/test_zoneinfo/test_zoneinfo.py

@@ -13,6 +13,7 @@
 import re
 import shutil
 import struct
+import sys
 import tempfile
 import types
 import unittest
@@ -2236,6 +2237,8 @@ def test_pydatetime(self):
             PYTHONTZPATH=str(ZONEINFO_DATA.tzpath))
 
 
+@unittest.skipIf(sys.modules.get("_zoneinfo") is None,
+                 "_zoneinfo C module not available")
 class ExtensionBuiltTest(unittest.TestCase):
     """Smoke test to ensure that the C and Python extensions are both tested.