How/when/which environment variables are passed to poetry and it's children

[Maciej-Zwolinski]

The reason I'm asking is that I need certain environment variable to be passed to a build process of one of my dependencies (from git). When using normal pip installation I'd run the following:

BUILD_ENV_VAR=val python3 -m pip install 'git+https://[...].git@version

Is there a way to achieve the same in poetry? For example BUILD_ENV_VAR=val poetry install?

On related topic, if I use poetry-dotenv-plugin to set my environment variables are they initiated before or after install, or only in poetry shell?