[lldb/test] Disable TestScriptedProcess.py unless Darwin

This patch disables TestScriptedProcess.py on Linux and Windows while I
investigate the OS specific failure:

http://lab.llvm.org:8011/#/builders/68/builds/19793

Signed-off-by: Med Ismail Bennani <medismail.bennani@gmail.com>

lldb/test/API/functionalities/scripted_process/TestScriptedProcess.py

@@ -88,6 +88,7 @@ def test_scripted_process_and_scripted_thread(self):
         for idx, reg in enumerate(registers, start=1):
             self.assertEqual(idx, int(reg.value, 16))
 
+    @skipUnlessDarwin
     def test_launch_scripted_process_stack_frames(self):
         """Test that we can launch an lldb scripted process from the command
         line, check its process ID and read string from memory."""