pythongh-111912: Run test_posix on Windows (pythonGH-111913)

(cherry picked from commit 64fea32)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>

Lib/test/test_posix.py

@@ -6,9 +6,6 @@
 from test.support import warnings_helper
 from test.support.script_helper import assert_python_ok
 
-# Skip these tests if there is no posix module.
-posix = import_helper.import_module('posix')
-
 import errno
 import sys
 import signal
@@ -22,6 +19,11 @@
 import textwrap
 from contextlib import contextmanager
 
+try:
+    import posix
+except ImportError:
+    import nt as posix
+
 try:
     import pwd
 except ImportError:
@@ -1009,6 +1011,7 @@ def test_environ(self):
             self.assertEqual(type(k), item_type)
             self.assertEqual(type(v), item_type)
 
+    @unittest.skipUnless(os.name == 'posix', "see bug gh-111841")
     def test_putenv(self):
         with self.assertRaises(ValueError):
             os.putenv('FRUIT\0VEGETABLE', 'cabbage')
@@ -1220,6 +1223,7 @@ def test_sched_setaffinity(self):
             self.assertRaises(OSError, posix.sched_setaffinity, -1, mask)
 
     @unittest.skipIf(support.is_wasi, "No dynamic linking on WASI")
+    @unittest.skipUnless(os.name == 'posix', "POSIX-only test")
     def test_rtld_constants(self):
         # check presence of major RTLD_* constants
         posix.RTLD_LAZY