Add a release workflow to GitHub Actions (astral-sh#257)

Add GitHub Actions workflow

pythonbuild: update default time in tar archives to 2024-01-01

Let's emit somewhat modern timestamps instead of times from 2021.

The new date is midnight in UTC not midnight in US/Pacific.

unix: normalize build configuration to aid portability

This commit implements a long desired feature to normalize the build
configuration in various distribution files post build but pre
packaging.

The goal of this general feature is to make distributions highly
portable. Before, configurations (which were used to e.g. compile
extension modules) referenced build environment paths, like `/tools`.
This is not desirable and can confuse downstream users when unexpected
settings are used.

The impetus for this work is astral-sh#194. As part of this change we strip the
`-fdebug-default-version` argument from `CFLAGS` to restore CFLAGS
compatibility with GCC.

There's no doubt additional settings that could be normalized. Those
can be implemented as follow-ups.

downloads: CPython 3.12.0rc3 -> 3.12.0

downloads: CPython 3.11.4 -> 3.11.5

We remove a patch for limits.h handling because upstream incorporated a
fix (from a bug report I filed).

And it looks like upstream backported build system changes to build with
OpenSSL 3.0 on Windows. We need to update our code accordingly.

We really should be building against OpenSSL 3.0. But that's scope
bloat. We'll get there.

requirements: update to latest

downloads: upgrade LLVM toolchains 16.0.2 -> 16.0.3

just: refactor macOS build script

Builds still intermittently fail a lot for me. So let's retry the
build once before giving up.

To avoid repetition we use a shell for loop.

unix: always disable mkfifoat and mknodat on 3.8

Newer Apple SDKs say that these are introduced in macOS 13.0. So we need
to ban them unconditionally on 3.8 since 3.8 doesn't support weak
linking.