cx_freeze support in addition to PyInstaller

[grokwithrahul]

I built my eel application using cx_freeze instead of PyInstaller, then realized that PyInstaller-specific variables were hardcoded into init.py. In the function _get_real_path, sys.frozen is used by both cx_freeze and PyInstaller. However, sys._MEIPASS is a variable that only PyInstaller uses (to store the current path of the folder). I added support to allow the users to say what their application is frozen with, during the eel.init(), with the variable frozen_with.

[samuelhwilliams]

Is there some benefit from using cx_Freeze over PyInstaller?