gh-136156: Allow using linkat() with TemporaryFile

tempfile.TemporaryFile() no longer uses os.O_EXCL with os.O_TMPFILE,
so it's possible to use linkat() on the file descriptor.

Author: vstinner

Lib/tempfile.py

@@ -656,7 +656,7 @@ def TemporaryFile(mode='w+b', buffering=-1, encoding=None,
             fd = None
             def opener(*args):
                 nonlocal fd
-                flags2 = (flags | _os.O_TMPFILE) & ~_os.O_CREAT
+                flags2 = (flags | _os.O_TMPFILE) & ~_os.O_CREAT & ~_os.O_EXCL
                 fd = _os.open(dir, flags2, 0o600)
                 return fd
             try:

Misc/NEWS.d/next/Library/2025-07-04-12-53-02.gh-issue-136156.OYlXoz.rst

@@ -0,0 +1,3 @@
+:func:`tempfile.TemporaryFile` no longer uses :data:`os.O_EXCL` with
+:data:`os.O_TMPFILE`, so it's possible to use ``linkat()`` on the file
+descriptor. Patch by Victor Stinner.