Log Message:
lang/python38: Fix for macOS 11 and Apple Silicon

(Apple Silicon being their aarch64 platform.)

This is backport of the same in lang/python39. Only minor changes were
needed.

Patches consist of:
 - Upstream work: https://github.com/python/cpython/pull/22855
 - Fix for setup.py to find libbz2.tbd and libz.tbd now that with the
   shared library cache there's nothing in /usr/lib.
   See: https://bugs.python.org/issue41116
 - Addition of __arch64__ case to fix _decimal module. A very similar fix
   has since been committed upstream.