Import ctypes.wintypes explicitly to avoid a python exception when child processes get hung.

build/automation.py.in

@@ -455,7 +455,7 @@ def environment(env = None, xrePath = DIST_BIN, crashreporter = True):
   return env
 
 if IS_WIN32:
-  import ctypes, time, msvcrt
+  import ctypes, ctypes.wintypes, time, msvcrt
   PeekNamedPipe = ctypes.windll.kernel32.PeekNamedPipe
   GetLastError = ctypes.windll.kernel32.GetLastError