Describe the issue:

The test TestNumpyConfig.test_configtool_pkgconfigdir fails during NumPy build in a virtual environment on systems where Python is configured with --with-platlibdir=lib64 and lib64 is a symlink to lib. The test compares a resolved pkgconfigdir path from _configtool.py (pointing to lib) with an unresolved PKG_CONFIG_DIR (pointing to lib64), causing an assertion error.

Reproduce the code example:

import subprocess
import pathlib
from numpy.tests.test_configtool import TestNumpyConfig, PKG_CONFIG_DIR

test = TestNumpyConfig()
stdout = test.check_numpyconfig('--pkgconfigdir')
assert pathlib.Path(stdout) == PKG_CONFIG_DIR

# Traceback (most recent call last):
#   File "<stdin>", line 1, in <module>
# AssertionError

Error message:

=================================== FAILURES ===================================
_________________ TestNumpyConfig.test_configtool_pkgconfigdir _________________

self = <numpy.tests.test_configtool.TestNumpyConfig object at 0x7f2b10463950>

    def test_configtool_pkgconfigdir(self):
        stdout = self.check_numpyconfig('--pkgconfigdir')
>       assert pathlib.Path(stdout) == PKG_CONFIG_DIR
E       AssertionError: assert PosixPath('/usr/src/RPM/BUILD/python3-module-numpy-2.3.1/.run_venv/lib/python3/site-packages/numpy/_core/lib/pkgconfig') == PosixPath('/usr/src/RPM/BUILD/python3-module-numpy-2.3.1/.run_venv/lib64/python3/site-packages/numpy/_core/lib/pkgconfig')
E        +  where PosixPath('/usr/src/RPM/BUILD/python3-module-numpy-2.3.1/.run_venv/lib/python3/site-packages/numpy/_core/lib/pkgconfig') = <class 'pathlib.Path'>('/usr/src/RPM/BUILD/python3-module-numpy-2.3.1/.run_venv/lib/python3/site-packages/numpy/_core/lib/pkgconfig')
E        +    where <class 'pathlib.Path'> = pathlib.Path

../.run_venv/lib64/python3/site-packages/numpy/tests/test_configtool.py:36: AssertionError

Python and NumPy Versions:

2.3.1
3.12.11 (main, Jul 12 2025, 16:50:29) [GCC 14.2.1 20241028 (ALT Sisyphus 14.2.1-alt1)]

Runtime Environment:

[{'numpy_version': '2.3.1',
'python': '3.12.11 (main, Jul 12 2025, 16:50:29) [GCC 14.2.1 20241028 (ALT '
'Sisyphus 14.2.1-alt1)]',
'uname': uname_result(system='Linux', node='localhost.localdomain', release='6.12.11-6.12-alt1', version='#1 SMP PREEMPT_DYNAMIC Fri Jan 31 06:35:42 UTC 2025', machine='x86_64')},
{'simd_extensions': {'baseline': ['SSE', 'SSE2', 'SSE3'],
'found': [],
'not_found': ['SSSE3',
'SSE41',
'POPCNT',
'SSE42',
'AVX',
'F16C',
'FMA3',
'AVX2',
'AVX512F',
'AVX512CD',
'AVX512_KNL',
'AVX512_KNM',
'AVX512_SKX',
'AVX512_CLX',
'AVX512_CNL',
'AVX512_ICL',
'AVX512_SPR']}},
{'architecture': 'Prescott',
'filepath': '/usr/lib64/libopenblasp-r0.3.30.so',
'internal_api': 'openblas',
'num_threads': 4,
'prefix': 'libopenblas',
'threading_layer': 'pthreads',
'user_api': 'blas',
'version': '0.3.30'}]

Context for the issue:

The failure occurs in build environments where Python is configured with --with-platlibdir=lib64 (e.g., ALT Linux), and lib64 is a symlink to lib, causing a path mismatch in the test.