The active.py script is currently clearing the IDF_PYTHON_ENV_PATH,
preventing it from being set to a custom location for the python virtual
environment directory. Although the install script checks to ensure that
an existing python virtual environment is not overwritten with one for a
different ESP-IDF version than it was originally created for, we should
still permit setting a custom path for the python virtual environment.
Closes https://github.com/espressif/esp-idf/issues/15006
Signed-off-by: Frantisek Hrbata <frantisek.hrbata@espressif.com>