Consider building wheel from sdist to ensure a proper sdist is created.

[BurningLutz]

Is your feature/enhancement proposal related to a problem? Please describe.

I have some Cython codes (.pyx files) in my project, and I use setuptools backend (the only backend supports building C extensions AFAIK) to compile them.

For source installation, those .pyx files should be included in sdist, but setuptools doesn't include them by default.

The problem is, currently pdm build will always succeed to build the sdist and the wheel even if those .pyx files are not included in the sdist, and the created sdist cannot be installed due to the lack of .pyx files.

Describe the solution you'd like

I suggest we first build the sdist, and then build the wheel from that sdist. This is the same approach as build.