Three tests added in #6220 use the `/sys/kernel/address_bits` file on Linux ([`test_cp_default_virtual_file()`](https://github.com/AnirbanHalder654322/coreutils/blob/c0c034232122b2501803bfdd0e90e7161b9a8af5/tests/by-util/test_cp.rs#L4096), [`test_cp_debug_sparse_always_sparse_virtual_file()`](https://github.com/AnirbanHalder654322/coreutils/blob/c0c034232122b2501803bfdd0e90e7161b9a8af5/tests/by-util/test_cp.rs#L4196), and [`test_cp_debug_default_sparse_virtual_file()`](https://github.com/AnirbanHalder654322/coreutils/blob/c0c034232122b2501803bfdd0e90e7161b9a8af5/tests/by-util/test_cp.rs#L4400)). This file was only [added a year ago](https://github.com/torvalds/linux/blob/5eb4573ea63d0c83bf58fb7c243fc2c2b6966c02/Documentation/ABI/testing/sysfs-kernel-address_bits#L2), so those tests are failing on any distro with a kernel older than that. E.g., I don't have that file on Debian 12 (bookworm). @AnirbanHalder654322, is there anything special about this file (other than being virtual) for those tests, and if so, are there any other older files that could be used instead?