when trying to build rc1 from a b4 venv to prepare a python host for cross compilation on ubuntu xenial flavour x64

i got :


cd /tmp
python3.7 -m venv testenv
cd testenv/
. bin/activate
(testenv) /tmp/testenv $ tar xf /tmp/Python-3.8.0rc1.tar.xz && cd Python-3.8.0rc1

CC=clang ./configure --prefix=/tmp/python3.host --with-system-ffi --disable-ipv6 --without-ensurepip --with-c-locale-coercion --disable-shared && make

./python -E ./setup.py  build
step will fail for the reason i suspect is srcdir is taken from system python3.8 if installed ( /usr/local in that case )

$ ./python -E 
Python 3.8.0rc1 (default, Oct  7 2019, 15:16:07) 
[Clang 6.0.0 (tags/RELEASE_600/final)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import sysconfig
>>> sysconfig.get_config_var('srcdir')
'/usr/local/lib/python3.8/config-3.8-x86_64-linux-gnu'
>>>