[3.12] gh-103224: Resolve paths properly in test_sysconfig (GH-103292) (GH-115100)

To pass tests when executed through a Python symlink.

(cherry picked from commit 71239d50b54c90afd3fdde260848e0c6d73a5c27)

Co-authored-by: Artem Mukhin <artem.m.mukhin@gmail.com>
Co-authored-by: Miro Hrončok <miro@hroncok.cz>