Check existence of SIGHUP before using it

[chying]

Summary

-SIGHUP doesn't exist on Windows

lldb/trunk/test/dosep.py

def process_dir_worker_multiprocessing(
         a_output_lock, a_test_counter, a_total_tests, a_test_name_len,
         a_dotest_options, job_queue, result_queue, inferior_pid_events,
         worker_index_map):
     """Worker thread main loop when in multiprocessing mode.
     Takes one directory specification at a time and works on it."""
 
     # Shut off interrupt handling in the child process.
     signal.signal(signal.SIGINT, signal.SIG_IGN)
+    if hasattr(signal, 'SIGHUP'):
         signal.signal(signal.SIGHUP, signal.SIG_IGN)
 
     # Setup the global state for the worker process.
     setup_global_variables(
         a_output_lock, a_test_counter, a_total_tests, a_test_name_len,
         a_dotest_options, worker_index_map)
 
     # Keep grabbing entries from the queue until done.
     while not job_queue.empty():
def main(print_details_on_success, num_threads, test_subdir,
     @param results_formatter if specified, provides the TestResultsFormatter
     instance that will format and output test result data from the
     side-channel test results.  When specified, inferior dotest calls
     will send test results side-channel data over a socket to the parallel
     test runner, which will forward them on to results_formatter.
     """
 
     # Do not shut down on sighup.
+    if hasattr(signal, 'SIGHUP'):
         signal.signal(signal.SIGHUP, signal.SIG_IGN)
 
     dotest_argv = sys.argv[1:]
 
     global output_on_success, RESULTS_FORMATTER
     output_on_success = print_details_on_success
     RESULTS_FORMATTER = results_formatter
 
     # We can't use sys.path[0] to determine the script directory