gh-109615: Fix support test_copy_python_src_ignore()

[vstinner]

Fix the test when run on an installed Python: use "abs_srcdir" of sysconfig, and skip the test if the Python source code cannot be found.

• Tools/patchcheck/patchcheck.py, Tools/freeze/test/freeze.py and Lib/test/libregrtest/utils.py now first try to get "abs_srcdir" from sysconfig, before getting "srcdir" from sysconfig.
• test.pythoninfo logs sysconfig "abs_srcdir".

• Issue: test_tools: test_freeze_simple_script() fails on s390x SLES 3.x: [Errno 2] No such file or directory: (...) #109615

[vstinner]

!buildbot aarch64 Fedora Stable Clang Installed

[bedevere-bot]

🤖 New build scheduled with the buildbot fleet by @vstinner for commit b9027a9 🤖

The command will test the builders whose names match following regular expression: aarch64 Fedora Stable Clang Installed

The builders matched are:

• aarch64 Fedora Stable Clang Installed PR

[miss-islington]

Thanks @vstinner for the PR 🌮🎉.. I'm working now to backport this PR to: 3.11, 3.12.
🐍🍒⛏🤖 I'm not a witch! I'm not a witch!

[miss-islington]

Sorry, @vstinner, I could not cleanly backport this to 3.12 due to a conflict.
Please backport using cherry_picker on command line.
cherry_picker b89ed9df39851348fbb1552294644f99f6b17d2c 3.12

[miss-islington]

Sorry, @vstinner, I could not cleanly backport this to 3.11 due to a conflict.
Please backport using cherry_picker on command line.
cherry_picker b89ed9df39851348fbb1552294644f99f6b17d2c 3.11

[bedevere-app]

GH-109962 is a backport of this pull request to the 3.11 branch.

[bedevere-bot]

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot wasm32-wasi 3.11 has failed when building commit 8ac20e5.

What do you need to do:

1. Don't panic.
2. Check the buildbot page in the devguide if you don't know what the buildbots are or how they work.
3. Go to the page of the buildbot that failed (https://buildbot.python.org/all/#builders/1047/builds/977) and take a look at the build logs.
4. Check if the failure is related to this commit (8ac20e5) or if it is a false positive.
5. If the failure is related to this commit, please, reflect that on the issue and make a new Pull Request with a fix.

You can take a look at the buildbot page here:

https://buildbot.python.org/all/#builders/1047/builds/977

Failed tests:

• test_support

Failed subtests:

• test_copy_python_src_ignore - test.test_support.TestSupport.test_copy_python_src_ignore

Summary of the results of the build (if available):

==

Click to see traceback logs

Traceback (most recent call last):
  File "/Lib/test/test_support.py", line 794, in test_copy_python_src_ignore
    self.assertEqual(support.copy_python_src_ignore(src_dir, names),
AssertionError: frozenset({'.git', '__pycache__'}) != {'build', '.git', '__pycache__'}

[bedevere-app]

GH-110340 is a backport of this pull request to the 3.12 branch.