test_python_executable failure on macOS 12.7.5

Test added in #120006 fails when running in my private buildbots.

Since it passed in CI, I suspect this means it was relying on the machine configuration or the presence of the source tree to get through the tests. The CI machine was running macOS-13.6.7-x86_64-i386-64bit-Mach-O and mine is macOS-12.7.5-x86_64-i386-64bit-Mach-O.

Mine also applies some install_name_tool modifications to the binaries and deploys them to a new machine before running tests, but given every other test passes and the failure here is to locate a Python module rather than a native one, I have to assume that's not impactful.

stderr:
---
Could not find platform independent libraries <prefix>
Could not find platform dependent libraries <exec_prefix>
Fatal Python error: Failed to import encodings module
Python runtime state: core initialized
ModuleNotFoundError: No module named 'encodings'

Current thread 0x0000000115121600 (most recent call first):
  <no Python frame>
---

I'm not in a position to test or debug, unfortunately. I see that Ned proposed to deprecate this variable entirely in #91057, so I wonder how badly we need this test?

#120006 で追加された test_python_executable テストから始め、報告書に記載された macOS 12.7.5 ビルドで再現してください。報告されている deployment と install_name_tool の違いを含め、その動作を macOS 13.6.7 の CI 環境と比較してください。encodings モジュールが見つからない原因を特定し、テストまたはその前提を変更する必要があるかどうかを明らかにできれば完了です。