Allow build options for dependencies

• [ x] I have searched the issues of this repo and believe that this is not a duplicate.
• [ x] I have searched the documentation and believe that my question is not covered.

Feature Request

Background

I am trying to use poetry to install detectron2 inside windows environment (binaries are only provided for linux/mac).

However detectron2 is still using setup.py and torch is an hard requirement inside the setup.py. This cuz the build to fail because poetry is installing in an isolated environment (fresh venv with no torch)

I noticed that build provides a flag for non-isolated environment for the build step.

If we can include some of the flags available to build (i.e. -n), i will be able to install and build detectron2 locally using poetry venv.

i.e.

[tool.poetry.dependencies]
detectron2 = {path = "<some-git-path>", isolated-build-env = false}
``

Start by tracing how Poetry builds path and Git dependencies in isolated environments, using the proposed isolated-build-env = false option and the build non-isolated flag as the expected behavior. Check how dependency configuration is parsed and passed to the build step, then verify that a legacy setup.py dependency requiring torch can build in the Poetry virtual environment without isolation.