Issue #26661: setup.py now detects system libffi with multiarch wrapper.

diff --cc Misc/NEWS
index 4bed3f0e9ccd7771a68b8a3623fbe6ff6942b14c,671a9b41c96bf21476fe4bcfe4f8850b86f6fc2e..0c36c2046885f80c48a3a8e793a7e502cc6ed519
--- 1/Misc/NEWS
--- 2/Misc/NEWS
+++ b/Misc/NEWS
@@@ -99,10 -93,8 +99,12 @@@ Window
  Build
  -----
  
+ - Issue #26661: setup.py now detects system libffi with multiarch wrapper.
+ 
 +- Issue #27979: A full copy of libffi is no longer bundled for use when
 +  building _ctypes on non-OSX UNIX platforms.  An installed copy of libffi is
 +  now required when building _ctypes on such platforms.
 +
  - Issue #15819: Remove redundant include search directory option for building
    outside the source tree.
  

diff --cc setup.py
Simple merge