Bug when using custom_hook to build extension and src layout

[I-love-study]

When using src layout, and with extension (using pdm_build_update_setup_kwargs hook and setuptools.Extension) After building success, pdm will get file from '.pdm-build' folder. But the layout in '.pdm-build' is not like src/package_name/xxx.py, is package_name/xxx.py, which will let includes and excludes not as expected. Like includes = ["src/package_name/*.py"]

Without building extension:

- Adding .pdm-build\package_name\__init__.py -> package_name/__init__.py
- Adding .pdm-build\package_name\__main__.py -> package_name/__main__.py
- ...

With building extension:

- Adding src\package_name\__init__.py -> package_name/__init__.py
- Adding src\package_name\__main__.py -> package_name/__main__.py
- ...

Sorry for the poor english.

[frostming]

All files are collected under .pdm-build unless excluded by excludes setting: https://github.com/pdm-project/pdm-backend/blob/6c48d72f0e41ae79749846471d18065925af79c6/src/pdm/backend/base.py#L269-L274