Issue #21166: merge from 3.4

diff --cc Makefile.pre.in
Simple merge

diff --cc Misc/NEWS
index bdc53c6a7640515033d39cb220e7abad85540def,97d42db153c9238b1c66e4b8c6b22cc7f90b4d75..da1fc32ac8bd558a230e558d1e3aa6d4c6d09b2f
--- 1/Misc/NEWS
--- 2/Misc/NEWS
+++ b/Misc/NEWS
@@@ -816,27 -643,8 +816,30 @@@ Buil
  - Issue #20644: OS X installer build support for documentation build changes
    in 3.4.1: assume externally supplied sphinx-build is available in /usr/bin.
  
 +- Issue #20022: Eliminate use of deprecated bundlebuilder in OS X builds.
 +
 +- Issue #15968: Incorporated Tcl, Tk, and Tix builds into the Windows build
 +  solution.
 +
 +- Issue #17095: Fix Modules/Setup *shared* support.
 +
 +- Issue #21811: Anticipated fixes to support OS X versions > 10.9.
 +
++- Issue #21166: Prevent possible segfaults and other random failures of
++  python --generate-posix-vars in pybuilddir.txt build target.
++
  C API
  -----
 +
 +- Issue #18395: Rename ``_Py_char2wchar()`` to :c:func:`Py_DecodeLocale`,
 +  rename ``_Py_wchar2char()`` to :c:func:`Py_EncodeLocale`, and document
 +  these functions.
 +
 +- Issue #21233: Add new C functions: PyMem_RawCalloc(), PyMem_Calloc(),
 +  PyObject_Calloc(), _PyObject_GC_Calloc(). bytes(int) is now using
 +  ``calloc()`` instead of ``malloc()`` for large objects which is faster and
 +  use less memory.
 +
  - Issue #20942: PyImport_ImportFrozenModuleObject() no longer sets __file__ to
    match what importlib does; this affects _frozen_importlib as well as any
    module loaded using imp.init_frozen().

diff --cc configure
Simple merge

diff --cc configure.ac
Simple merge