Citing https://www.postgrespro.ru/list/id/E1kfzRR-0001EH-Ph@gemulon.postgresql.org
fixing the same problem:
We previously put the -isysroot switch only into CPPFLAGS, theorizing
that it was only needed to find the right copies of include files.
However, it seems that we also need to use it while linking programs,
to find the right stub ".tbd" files for libraries.  We got away
without that up to now, but apparently that was mostly luck.  It may
also be that failures are only observed when the Xcode version is
noticeably out of sync with the host macOS version; the case that's
prompting action right now is that builds fail when using latest Xcode
(12.2) on macOS Catalina, even though it's fine on Big Sur.

Specifically, the problem arises for `preadv' and `pwritev' (new in MacOS 11 Big Sur) when building with XCode 12.4 (supporting Big Sur) in MacOS 10.15 Catalina.

https://www.gnu.org/server/mirror.html advises
to use http://ftpmirror.gnu.org/
for automatic mirror selection

Use tclConfig.sh/tkConfig.sh for future-proofing
3.14.0 doesn't detect Tcl/Tk with external libtommath, have to do it ourselves

---------

Co-authored-by: Ivan Pozdeev <vano@mail.mipt.ru>

Tcl/Tk 9.0 support was added in 3.13.0b3 and is not official as of 3.14.0;
the build with Homebrew version fails as of this writing

Fixes warnings "configure: WARNING: unrecognized options: --with-tcltk-libs, --with-tcltk-includes"

fix script

Apple CLang excludes it if -isysroot is passed

use global setup with bats with possibility to add specific test file _setup
use readlink in helper if realpath is not working as expected

fix bats warnings

Make sur that PYENV_TEST_DIR is created if mktemp failed
mock python3 usage by updating create_executable function
fix test by adding the right PATH
update path in plugin test
replace for loop with while read
don't use symlink for stub

* Fix specifying XCode SDK for distutils

* Revert to preferring XCode Zlib

It turns out, everything since 2.7.12 and 3.5.2
can use libs from modern XCode SDK
which is always available unless we're using an alternate compiler

Zlib from XCode is virtually always present now so it only makes sense to use it from elsewhere if it's preferred.
Works around build failure for 2.7 that's incapable of using Zlib from XCode 7+ (see #3301)

miniforge-25.3.0-0 is marked as prerelease, there's no Linux version. Probably recalled.

* use `xcrun` instead of `xcodebuild` which is absent in CLT
* use an alternative way that's compatible with CPython's setup.py since 3.5.2

---------

Co-authored-by: Ivan Pozdeev <vano@mail.mipt.ru>

It breaks the build due to yet unknown structural changes from XCode 15