gh-95174: Handle missing dup() and constants in WASI (GH-95229)

- check for ``dup()`` libc function
- handle missing ``F_DUPFD`` in ``dup2()`` replacement function
- add workaround for WASI libc bug in MSG_TRUNC
- ESHUTDOWN is missing, use EPIPE instead
- POLLPRI is missing, define as 0 (no-op)

Modules/selectmodule.c

@@ -63,6 +63,11 @@ extern void bzero(void *, int);
 #  define SOCKET int
 #endif
 
+// WASI SDK 16 does not have POLLPRIO, define as no-op
+#if defined(__wasi__) && !defined(POLLPRI)
+#  define POLLPRI 0
+#endif
+
 typedef struct {
     PyObject *close;
     PyTypeObject *poll_Type;