I just tested on a fresh macOS 10.15.3 Virtual Machine (on the same host machine as the one of previous messages) and I can reproduce the problem: 

1. Install Command Line Tools (xcode-build --install)
2. Download Python 3.8.1
3. Extract tarball
4. Create a file make.py with the following python code
```
import subprocess

subprocess.run(["./configure"])
subprocess.run(["make", "-j4"])
```
and save it in the Python-3.8.1 source tree
6. Create a venv doing `python -m venv venv` in the source tree
7. Activate the virtual env `source venv/bin/activate`
5. Run it doing `python3 make.py`

The build fails with the error described before. 

If you now, instead, run the make directly `make -j8` the buids proceeds as expected.