test_dir_seek is failing on main

[sunfishcode]

@nrath-js The test_dir_seek test is failing on main on arm on the libc backend:

https://github.com/bytecodealliance/rustix/actions/runs/12680283634/job/35341748535

It's possible this is related to a 64-bit offset being casted to a 32-bit c_long for the seekdir call. Do you know of any alternative we might use here?

If there aren't any other alternatives, we may have to revert this feature.