better-pyvenv-fix

[jhheider]

--copies breaks darwin:

+ git tag -a 9.1.0 -m 'Version 9.1.0' --force
+ unset GIT_DIR
+ '[' '' = poetry ']'
+ python -m venv --copies /opt/pytest.org/v9.1.0+brewing/venv
Error: Command '['/opt/pytest.org/v9.1.0+brewing/venv/bin/python', '-m', 'ensurepip', '--upgrade', '--default-pip']' died with <Signals.SIGABRT: 6>.

[Copilot]

Pull request overview

This PR addresses a macOS/Darwin failure when creating Python virtual environments with python -m venv --copies, by selecting a platform-appropriate venv creation mode in bkpyvenv.

Changes:

• Use python -m venv --copies on Linux to avoid absolute-symlink relocation issues.
• Use default python -m venv on non-Linux (eg macOS) to avoid --copies breaking signed/framework Python binaries.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.