Fixes Issue #27983: Cause lack of llvm-profdata tool when using clang as

required for PGO linking to be a configure time error rather than
make time when --with-optimizations is enabled.  Also improve our
ability to find the llvm-profdata tool on MacOS and some Linuxes.

diff --cc Misc/NEWS
index 71598b7c473e05bacab801b8d4860dfe225b8c07,31bf8157547e33854b28980c981b5d8a4aabc937..de45fc95ab6f75e15532d4095cc1102fe0bee551
--- 1/Misc/NEWS
--- 2/Misc/NEWS
+++ b/Misc/NEWS
@@@ -10,39 -10,13 +10,44 @@@ What's New in Python 3.6.0 beta 
  Core and Builtins
  -----------------
  
+ - Issue #27983: Cause lack of llvm-profdata tool when using clang as
+   required for PGO linking to be a configure time error rather than
+   make time when --with-optimizations is enabled.  Also improve our
+   ability to find the llvm-profdata tool on MacOS and some Linuxes.
+ 
  - Issue #26307: The profile-opt build now applys PGO to the built-in modules.
  
 +- Issue #27078: Added BUILD_STRING opcode.  Optimized f-strings evaluation.
 +
 +- Issue #17884: Python now requires systems with inttypes.h and stdint.h
 +
 +- Issue #27961: Require platforms to support ``long long``. Python hasn't
 +  compiled without ``long long`` for years, so this is basically a formality.
 +
 +- Issue #27355: Removed support for Windows CE.  It was never finished,
 +  and Windows CE is no longer a relevant platform for Python.
 +
 +- Issue #27921: Disallow backslashes in f-strings. This is a temporary
 +  restriction: in beta 2, backslashes will only be disallowed inside
 +  the braces (where the expressions are). This is a breaking change
 +  from the 3.6 alpha releases.
 +
 +- Implement PEP 523.
 +
 +- Issue #27870: A left shift of zero by a large integer no longer attempts
 +  to allocate large amounts of memory.
 +
 +- Issue #25402: In int-to-decimal-string conversion, improve the estimate
 +  of the intermediate memory required, and remove an unnecessarily strict
 +  overflow check. Patch by Serhiy Storchaka.
 +
 +- Issue #27214: In long_invert, be more careful about modifying object
 +  returned by long_add, and remove an unnecessary check for small longs.
 +  Thanks Oren Milman for analysis and patch.
 +
 +- Issue #27506: Support passing the bytes/bytearray.translate() "delete"
 +  argument by keyword.
 +
  - Issue #27812: Properly clear out a generator's frame's backreference to the
    generator to prevent crashes in frame.clear().
  

diff --cc configure
Simple merge

diff --cc configure.ac
Simple merge