maintainer-feedback requested: [Bug 258377] lang/python36 lang/python37 lang/python38 lang/python39 lang/python310: disable detection of multiarch for clang 13

Bugzilla Automation <bugzilla@FreeBSD.org> has asked freebsd-python (Nobody)
<python@FreeBSD.org> for maintainer-feedback:
Bug 258377: lang/python36 lang/python37 lang/python38 lang/python39
lang/python310: disable detection of multiarch for clang 13
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=258377



--- Description ---
During an exp-run for llvm 13 (see bug 258209), it turned out that
lang/python3([6-9]|10) do not build with clang 13.0.0 [1][2][3][4][5]:

LD_LIBRARY_PATH=/wrkdirs/usr/ports/lang/python36/work/Python-3.6.14 CC='cc'
LDSHARED='cc -shared  -lpthread -L/usr/local/lib  -fstack-protector-strong   '
OPT='-DNDEBUG'	_TCLTK_INCLUDES='' _TCLTK_LIBS=''  ./python -E ./setup.py -q
build
Failed to import the site module
Traceback (most recent call last):
  File "/wrkdirs/usr/ports/lang/python36/work/Python-3.6.14/Lib/site.py", line
553, in <module>
    main()
  File "/wrkdirs/usr/ports/lang/python36/work/Python-3.6.14/Lib/site.py", line
539, in main
    known_paths = addusersitepackages(known_paths)
  File "/wrkdirs/usr/ports/lang/python36/work/Python-3.6.14/Lib/site.py", line
282, in addusersitepackages
    user_site = getusersitepackages()
  File "/wrkdirs/usr/ports/lang/python36/work/Python-3.6.14/Lib/site.py", line
258, in getusersitepackages
    user_base = getuserbase() # this will also set USER_BASE
  File "/wrkdirs/usr/ports/lang/python36/work/Python-3.6.14/Lib/site.py", line
248, in getuserbase
    USER_BASE = get_config_var('userbase')
  File "/wrkdirs/usr/ports/lang/python36/work/Python-3.6.14/Lib/sysconfig.py",
line 601, in get_config_var
    return get_config_vars().get(name)
  File "/wrkdirs/usr/ports/lang/python36/work/Python-3.6.14/Lib/sysconfig.py",
line 550, in get_config_vars
    _init_posix(_CONFIG_VARS)
  File "/wrkdirs/usr/ports/lang/python36/work/Python-3.6.14/Lib/sysconfig.py",
line 421, in _init_posix
    _temp = __import__(name, globals(), locals(), ['build_time_vars'], 0)
ModuleNotFoundError: No module named
'_sysconfigdata_m_freebsd14_x86_64-unknown-freebsd14'
*** Error code 1

The reason this breaks with clang >= 13, is that it now started supporting the
-print-multiarch option, but in its output it adds a major.minor version
number, for example x86_64-unknown-freebsd14.0. The dot confuses Python, as it
appends the multiarch name to the sysconfig module name, and then can't load
the resulting _sysconfigdata__freebsd14_x86_64-unknown-freebsd14.0.py file:

    ModuleNotFoundError: No module named
'_sysconfigdata__freebsd14_x86_64-unknown-freebsd14'

Since we do not support multiarch, and the configure script has no way to
disable the multiarch check, I would like to propose to just stub it out during
post-patch, as per the attached diff.

[1]
http://gohan04.nyi.freebsd.org/data/mainamd64PR258209-default/2021-09-05_20h27m
09s/logs/errors/python36-3.6.14.log
[2]
http://gohan04.nyi.freebsd.org/data/mainamd64PR258209-default/2021-09-05_20h27m
09s/logs/errors/python37-3.7.11.log
[3]
http://gohan04.nyi.freebsd.org/data/mainamd64PR258209-default/2021-09-05_20h27m
09s/logs/errors/python38-3.8.11.log
[4]
http://gohan04.nyi.freebsd.org/data/mainamd64PR258209-default/2021-09-05_20h27m
09s/logs/errors/python39-3.9.7.log
[5]
http://gohan04.nyi.freebsd.org/data/mainamd64PR258209-default/2021-09-05_20h27m
09s/logs/errors/python310-3.10.0.r1.log