Issue #9433: The "-j" option to regrtest now works under Windows too.

It is not sure it will be beneficial, though, since process launching is
more expensive under Windows than it is under Linux.

Lib/test/regrtest.py

@@ -547,7 +547,8 @@ def main(tests=None, testdir=None, verbose=0, quiet=False,
                     popen = Popen([sys.executable, '-E', '-m', 'test.regrtest',
                                    '--slaveargs', json.dumps(args_tuple)],
                                    stdout=PIPE, stderr=PIPE,
-                                   universal_newlines=True, close_fds=True)
+                                   universal_newlines=True,
+                                   close_fds=(os.name != 'nt'))
                     stdout, stderr = popen.communicate()
                     # Strip last refcount output line if it exists, since it
                     # comes from the shutdown of the interpreter in the subcommand.