test_build_details fails if executed from a relocated place

Bug report

Bug description:

[2025-05-08T15:36:07.483Z] 0:00:57 load avg: 32.60 [ 90/491/1] test_bool passed
[2025-05-08T15:36:07.747Z] 0:00:57 load avg: 32.60 [ 91/491/2] test_build_details failed (1 failure)
[2025-05-08T15:36:07.747Z] test_base_interpreter (test.test_build_details.CPythonBuildDetailsTests.test_base_interpreter) ... FAIL
[2025-05-08T15:36:07.747Z] test_base_prefix (test.test_build_details.CPythonBuildDetailsTests.test_base_prefix) ... ok
[2025-05-08T15:36:07.747Z] test_implementation (test.test_build_details.CPythonBuildDetailsTests.test_implementation) ... ok
[2025-05-08T15:36:07.747Z] test_language_version (test.test_build_details.CPythonBuildDetailsTests.test_language_version) ... ok
[2025-05-08T15:36:07.747Z] test_language_version_info (test.test_build_details.CPythonBuildDetailsTests.test_language_version_info) ... ok
[2025-05-08T15:36:07.747Z] test_location (test.test_build_details.CPythonBuildDetailsTests.test_location) ... ok
[2025-05-08T15:36:07.747Z] test_parse (test.test_build_details.CPythonBuildDetailsTests.test_parse) ... ok
[2025-05-08T15:36:07.747Z] test_platform (test.test_build_details.CPythonBuildDetailsTests.test_platform) ... ok
[2025-05-08T15:36:07.747Z] test_top_level_container (test.test_build_details.CPythonBuildDetailsTests.test_top_level_container) ... ok
[2025-05-08T15:36:07.747Z] 
[2025-05-08T15:36:07.747Z] ======================================================================
[2025-05-08T15:36:07.747Z] FAIL: test_base_interpreter (test.test_build_details.CPythonBuildDetailsTests.test_base_interpreter)
[2025-05-08T15:36:07.747Z] ----------------------------------------------------------------------
[2025-05-08T15:36:07.747Z] Traceback (most recent call last):
[2025-05-08T15:36:07.747Z]   File "/bb/jenkins_work/python/workspace/python_python3.14-debian_PR-1/distro/refroot/amd64/opt/bb/lib64/python3.14/test/test_build_details.py", line 124, in test_base_interpreter
[2025-05-08T15:36:07.747Z]     self.assertEqual(os.path.realpath(value), os.path.realpath(sys.executable))
[2025-05-08T15:36:07.747Z]     ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[2025-05-08T15:36:07.747Z] AssertionError: '/bb/bin/package/opt/bb/bin/python3.14' != '/bb/jenkins_work/python/workspace/python_pyth[57 chars]3.14'
[2025-05-08T15:36:07.747Z] - /bb/bin/package/opt/bb/bin/python3.14
[2025-05-08T15:36:07.747Z] + /bb/jenkins_work/python/workspace/python_python3.14-debian_PR-1/distro/refroot/amd64/opt/bb/bin/python3.14
[2025-05-08T15:36:07.747Z] 
[2025-05-08T15:36:07.747Z] 
[2025-05-08T15:36:07.747Z] ----------------------------------------------------------------------
[2025-05-08T15:36:07.747Z] Ran 9 tests in 0.013s```


### CPython versions tested on:

3.14

### Operating systems tested on:

Linux

Start with test/test_build_details.py, especially CPythonBuildDetailsTests.test_base_interpreter, and reproduce the failure when Python is executed from a relocated installation. Inspect how the test obtains and compares the base interpreter paths. Done means test_build_details passes in the relocated-place scenario without breaking the other listed tests.