Resolve issue with incorrect .pyd file extension generation

[MrDengDengDeng]

No description provided.

[wjakob]

Related to issue #773.

[wjakob]

I am hesitant to merge this PR because there seem to be some platform-specific differences that aren't handled by this change.

On my macOS machine, the SOABI tag is cpython-312-darwin. So with two dashes, rather than a dash and an underline.

[MrDengDengDeng]

If so, you should use different rules in cmake for different platforms

[wjakob]

Let me add @henryiii, who wrote this line originally. I started to look into this and became quite confused.

On my macOS laptop, the suffix is .cpython-312-darwin.so. On Windows, it seems to be of the form .cp311-win_amd64.pyd. This page presents yet another naming scheme https://peps.python.org/pep-0425/ (but is outdated), and the current version seems in disagreement as well: https://packaging.python.org/en/latest/specifications/platform-compatibility-tags/#platform-compatibility-tags.

What are these version tags actually supposed to look like? What's the right combination of dashes and underscores to detect a compatible form and have the right mechanism for Scikit-build and PyPy?