Fix memory access violation on windows cp36/cp38

[LmeSzinc]

1. Fixed unittest process terminated on windows cp36/cp38

  Successfully installed zstd-1.5.7.3
  + python -m unittest discover -v -s D:\a\python-zstd\python-zstd
                                                              ✕ 4.95s
Error: Command python -m unittest discover -v -s D:\a\python-zstd\python-zstd
 failed with code 3221225477. None

2. Updated get-pip url since python3.9 is EOL

2026-05-05 22:02:01 (166 MB/s) - ‘get-pip.py’ saved [2226394/2226394]
ERROR: This script does not work on Python 3.9. The minimum supported Python version is 3.10. Please use https://bootstrap.pypa.io/pip/3.9/get-pip.py instead.
/usr/bin/pypy3.9: No module named pip (to install pip, you need to run once "/usr/bin/pypy3.9 -m ensurepip")
Error: Process completed with exit code 1.

The following tests still fails:

# Build wheel - Ubuntu 24+16 i386 CPython 2.7
Run sudo mkdir -p ./ubuntu-bionic-armhf/build_wheel
chroot: failed to run command ‘/usr/bin/apt’: No such file or directory
Error: Process completed with exit code 127.

# Build wheel - Ubuntu 24+20 i386 CPython 3.10
Building dependency tree...
You might want to run 'apt --fix-broken install' to correct these.
The following packages have unmet dependencies:
 console-setup-linux : Depends: kbd (>= 0.99-12) but it is not installable or
                                console-tools (>= 1:0.2.3-16) but it is not installable
 python3-pymacaroons : Depends: python3-nacl (>= 1.1.2) but it is not installable
E: Unmet dependencies. Try 'apt --fix-broken install' with no packages (or specify a solution).
Error: Process completed with exit code 100.

which should be an easy fix. So I keep this PR in minimal.

[sergey-dryabzhinsky]

Thanks for trigger that python3.9 getting older for get-pip.py.