Build should use a Python virtual environment

[dpaulat]

The current build process works, but relies on user-level configuration, which may present conflicts or configuration issues. A Python virtual environment would set up a dedicated Python environment for building Supercell Wx, creating a more consistent build experience.

• Define a virtual environment to use with building Supercell Wx
• Integrate with CMake to the greatest extent feasible
• Consider FindPython3: https://cmake.org/cmake/help/latest/module/FindPython3.html
• Investigate defining pip install requirements in CMakeLists.txt or CMake include, instead of a setup script
  • This could eliminate confusion of Python installations between the setup scripts and CMake environment