gh-103510: Support os.mkfifo on Windows

Make os.mkfifo return an open fd on Windows and the original path object
on Unix. The user would then pass the return value into open, which
accepts both path and fd as file.

Author: SuibianP

Modules/clinic/posixmodule.c.h

@@ -12523,7 +12523,7 @@ os_splice_impl(PyObject *module, int src, int dst, Py_ssize_t count,
 }
 #endif /* HAVE_SPLICE*/
 
-#ifdef HAVE_MKFIFO
+#if defined(HAVE_MKFIFO) || defined(MS_WINDOWS)
 /*[clinic input]
 os.mkfifo
 
@@ -12544,6 +12544,21 @@ static PyObject *
 os_mkfifo_impl(PyObject *module, path_t *path, int mode, int dir_fd)
 /*[clinic end generated code: output=ce41cfad0e68c940 input=73032e98a36e0e19]*/
 {
+#ifdef MS_WINDOWS
+    HANDLE h;
+    int fd;
+    Py_BEGIN_ALLOW_THREADS
+    h = CreateNamedPipeW(path->wide,
+        PIPE_ACCESS_DUPLEX | FILE_FLAG_FIRST_PIPE_INSTANCE,
+        PIPE_TYPE_BYTE | PIPE_READMODE_BYTE | PIPE_WAIT,
+        1, 1024, 1024, 0, NULL
+    );
+    Py_END_ALLOW_THREADS
+    if (INVALID_HANDLE_VALUE == h)
+        return win32_error_object("CreateNamedPipeW", path->object);
+    fd = _Py_open_osfhandle(h, _O_RDWR);
+    return PyLong_FromLong(fd);
+#else
     int result;
     int async_err = 0;
 #ifdef HAVE_MKFIFOAT
@@ -12578,7 +12593,8 @@ os_mkfifo_impl(PyObject *module, path_t *path, int mode, int dir_fd)
     if (result != 0)
         return (!async_err) ? posix_error() : NULL;
 
-    Py_RETURN_NONE;
+    return Py_NewRef(path->object);
+#endif
 }
 #endif /* HAVE_MKFIFO */