Building on Python 3.12 requires setuptools >=67

[rmartin16]

This is as much an FYI as anything, I suppose.

I was messing around with package building and noticed setuptools_scm >=8 recommends (err...requires...) setuptools >=64. Out of curiosity, I tried to build Briefcase with setuptools ==60 using Python 3.12 but it bombs out in setuptools on some import of nonexistent code. I bumped setuptools until the build would work and landed at >=67.

For any of our purposes, this doesn't really matter since the latest version of setuptools will always be used. However, if someone tried to package Briefcase themselves, the current setuptools version constraint isn't really truthful.

Furthermore, if you were following greg's recent chain about moving to pyproject.toml, he pointed out that pinning build requirements can create downstream problems. So, while Briefcase is unlikely to be a dependency for anything....it doesn't generally seem reliable to use pinning here 😕

At any rate...this'll make the setuptools build version constraint a little more truthful.

PR Checklist:

• All new features have been tested
• All new features have been documented
• I have read the CONTRIBUTING.md file
• I will abide by the code of conduct

[freakboy3742]

All makes sense.