Fix the new test on windows (skip it, its posix only)

Lib/test/test_subprocess.py

@@ -774,6 +774,7 @@ class ProcessTestCaseNoPoll(ProcessTestCase):
 
 
 class HelperFunctionTests(unittest.TestCase):
+    @unittest.skipIf(mswindows, "errno and EINTR make no sense on windows")
     def test_eintr_retry_call(self):
         record_calls = []
         def fake_os_func(*args):