Windows build should not require pre-installed Python

[Tom Goddard]

In order to encourage outside developers our Windows build should not require that Python is already installed. Specifically we currently require Python 3.7.4. To get the Windows build to work I had to uninstall the new Python 3.7.6 so I could install Python 3.7.4 in order for ChimeraX to build Python 3.7.4. This seems highly discouraging to any outside developer. If we are building Python we should not require that it is already installed.

[Greg Couch]

Tom, I believe you fixed this by creating a python-3.8.5-win-amd64.tar.bz2 file. I don't see a make file target for creating that tar file, just an upload_new_version target to use after the tar file has been created. Python 3.8.6 is out. Can you describe what you did so I can make the target and update Python? You're also welcome to do it.

[goddard@…]

I just installed the Python 3.8.x distribution on a Windows 10 machine and tarred the installed directory.  Not sure what the directory name needs to be, check the current one and Makefile to figure that out.  I was planning to do an update to Python 3.8.6 on all platforms, but if you get to it before me that is fine.  I was hoping 3.8.6 would eliminate the need for the PyOpenGL patch on Big Sur since that was really a Python ctypes bug.

[goddard@…]

Python 3.8.7 is expected out Dec 21 so might wait and jump to that version.

https://www.python.org/dev/peps/pep-0569/

[Greg Couch]

Switched to Python 3.8.7. Used the "make_win_distribution" target in prereqs/Python/Makefile to generate the tar file and the "upload_new_version" target to make it available.