Skip ioctl TCXONC tests on non-Linux.

Author: serhiy-storchaka

Lib/test/test_ioctl.py

@@ -168,6 +168,7 @@ def test_ioctl_clear_input_or_output(self):
         os.write(wfd, b'ABCDEF')
         self.assertEqual(os.read(rfd, 1024), b'ABCDEF')
 
+    @unittest.skipUnless(sys.platform == 'linux', 'only works on Linux')
     @unittest.skipUnless(hasattr(termios, 'TCXONC'), 'requires termios.TCXONC')
     def test_ioctl_suspend_and_resume_output(self):
         wfd = self.slave_fd