#6416: Fix compilation of the select module on Windows, as well as test_subprocess:
PIPE_BUF is not defined on Windows, and probably has no meaning there.
Anyway the subprocess module uses another way to perform non-blocking reads (with a thread)
diff --git a/Modules/selectmodule.c b/Modules/selectmodule.c
index a405812..d8a68c5 100644
--- a/Modules/selectmodule.c
+++ b/Modules/selectmodule.c
@@ -1746,7 +1746,9 @@
Py_INCREF(SelectError);
PyModule_AddObject(m, "error", SelectError);
+#ifdef PIPE_BUF
PyModule_AddIntConstant(m, "PIPE_BUF", PIPE_BUF);
+#endif
#if defined(HAVE_POLL)
#ifdef __APPLE__