Fix build issues when Python with free-threading is used

[smuzaffar]

Building pasparser with pythin 3.14 (free-threading enabled) failed with error [a]. This change allows to find the correct lib.linux-x86_64-cpython-314t' lib

[a]

Build dir: %s pacparser/src/../tests/../src/pymod/build
['lib.linux-x86_64-cpython-314t', 'temp.linux-x86_64-cpython-314t']
Traceback (most recent call last):
  File "pacparser/src/../tests/runtests.py", line 39, in runtests
    pacparser_module_path = module_path(tests_dir)
  File "pacparser-/src/../tests/runtests.py", line 35, in module_path
    return glob.glob(os.path.join(builddir, 'lib*%s' % py_ver))[0]
           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^
IndexError: list index out of range

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "pacparser/src/../tests/runtests.py", line 88, in <module>
    main()
    ~~~~^^
  File "pacparser/src/../tests/runtests.py", line 85, in main
    runtests(pacfile, testdata, tests_dir)
    ~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "pacparser/src/../tests/runtests.py", line 41, in runtests
    raise Exception('Tests failed. Could not determine pacparser path.')