configs: faux-filesystem fix w/ ruby in se mode

configs: faux-filesystem fix w/ ruby in se mode

These changes are needed so that the config scripts
can report cache hierarchy information to the faux
filesystem.

This is useful for the ROCm runtime when it reads
psuedofiles from the host filesytem from "/proc".

Change-Id: Iad3e6c088d47c9b93979f584de748367eae8259b
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/12121
Reviewed-by: Brandon Potter <Brandon.Potter@amd.com>
Maintainer: Brandon Potter <Brandon.Potter@amd.com>
Tested-by: kokoro <noreply+kokoro@google.com>