Failure during build of Python 3.8 via cygport

[Mark Geisert <mark@maxrnd.com>]

Hi Marco,
I was building Python locally so I can later submit a patch against it.  It 
appears the local python.exe was built successfully, but a later step failed with:

> ./python.exe -E -S -m sysconfig --generate-posix-vars ;\
> if test $? -ne 0 ; then \
>         echo "generate-posix-vars failed" ; \
>         rm -f ./pybuilddir.txt ; \
>         exit 1 ; \
> fi
> Traceback (most recent call last):
>   File "/usr/src/python38-3.8.3-1.src/python38-3.8.3-1.x86_64/src/Python-3.8.3/Lib/runpy.py", line 194, in _run_module_as_main
>     return _run_code(code, main_globals, None,
>   File "/usr/src/python38-3.8.3-1.src/python38-3.8.3-1.x86_64/src/Python-3.8.3/Lib/runpy.py", line 87, in _run_code
>     exec(code, run_globals)
>   File "/usr/src/python38-3.8.3-1.src/python38-3.8.3-1.x86_64/src/Python-3.8.3/Lib/sysconfig.py", line 711, in <module>
>     _main()
>   File "/usr/src/python38-3.8.3-1.src/python38-3.8.3-1.x86_64/src/Python-3.8.3/Lib/sysconfig.py", line 699, in _main
>     _generate_posix_vars()
>   File "/usr/src/python38-3.8.3-1.src/python38-3.8.3-1.x86_64/src/Python-3.8.3/Lib/sysconfig.py", line 416, in _generate_posix_vars
>     f.write(pybuilddir)
> UnicodeEncodeError: 'utf-8' codec can't encode characters in position 17-19: surrogates not allowed
> generate-posix-vars failed
> make: *** [Makefile:592: pybuilddir.txt] Error 1
> *** ERROR: make failed

I've seen UnicodeEncodeError before and searched and found how to fix it.. but 
hitting the issue while building Python itself seems more fraught.  Is this a 
known issue with known fix?
Thank you,

..mark