When Cython's --generate-shared feature is used, the path
/tmp/tmp[random]/_cyutility.pyx is embedded into the resulting
_cyutility*.so, making it unreproducible.

This feature is currently used by scipy and sklearn, and by the version
of pandas in Salsa (but not the version in the archive).

Possibly related: #1113976 was a similar bug affecting mesonpy + cython
packages more broadly, and was fixed by fixing the path.