[3.13] gh-153711: Avoid use of dup3 and pipe2 calls introduced in macOS 27 (#155211)

This prevents potential segfaults when builds are used on older
systems and avoids adding new code for supporting weaklinking.

Author: ned-deily

Misc/NEWS.d/next/macOS/2026-08-05-02-02-33.gh-issue-153711.pO9fFb.rst

@@ -0,0 +1,3 @@
+On macOS, do not attempt to use the :manpage:`dup3(2)` and
+:manpage:`pipe2(2)` system calls introduced in
+macOS 27 to prevent problems when running on older systems.

configure

@@ -5282,7 +5282,13 @@ fi
 # header definition prevents usage - autoconf doesn't use the headers), or
 # raise an error if used at runtime. Force these symbols off.
 if test "$ac_sys_system" != "iOS" ; then
-  AC_CHECK_FUNCS([dup3 getentropy getgroups pipe2 system])
+  AC_CHECK_FUNCS([getentropy getgroups system])
+fi
+# In addition, macOS introduced dup3 and pipe2 in macOS 27, late in the
+# lifetime of this version of Python. Rather than adding weaklinking
+# support for them, just continue to ignore them.
+if test "$ac_sys_system" != "iOS" -a "$ac_sys_system" != "Darwin"; then
+  AC_CHECK_FUNCS([dup3 pipe2])
 fi
 
 AC_CHECK_DECL([dirfd],