• I have searched the issues of this repo and believe that this is not a duplicate.
• I have searched the FAQ and general documentation and believe that my question is not already covered.

Feature Request

If using the (currently undocumented) build script feature as so:

[tool.poetry.build]
script = "build.py"
generate-setup-file = true

with a build script that has conditional library building as follows:

import os

from mypyc.build import mypycify

extensions = []

if os.environ.get("MYPYCIFY_BUILD", "False").lower() == "true":
    modules = [
        "my_package/submod1/foo.py",
        ...
        "my_package/submodn/bar.py",
    ]
    extensions = mypycify(modules)


def build(setup_kwargs):
    setup_kwargs.update(
        {
            "ext_modules": extensions,
        }
    )

Running poetry build always builds a plaform specific wheel (i.e. "my-package-0.1.1-cp310-cp310-manylinux_2_35_x86_64.whl") even if I specify (by env variable MYPYCIFY_BUILD=True).

It would be better if not specifying any ext_modules results in a non platform wheel like "my-package-0.1.1-py3-none-any.whl".