Build RV using a Python virtual environment

[chxmberland]

Linked issues

N/A

Summarize your change.

The Python version included with MacOS Sonoma 14.5 adopted PEP 668, which is meant to prevent conflicts between system level Python packages with project specific Python packages, like what is included in requirements.txt.

This means that the user will encounter an error when attempting to install Python requirements unless they use the tag --break-system-packages tag. By using a virtual environment, system-level conflicts are avoided and the user has a safer build of Open RV.

Describe what you have tested and on which operating system.

Mac OS Sonoma 14.5 and Windows 11.

If possible, provide screenshots.

PEP 668 error without a virtual environment, triggered by running rvbuild.