tests: Add --host tag

tests: Add --host tag

A host tag has been added to take into consideration the host ISA which
is running gem5 (default is X86).
There might be regressions which are supposed to be run on a particular
host machine only. This could be the case of dynamically linked
regressions which require dynamic linker/loader + shared libraries of
the same ISA as the target.

Change-Id: I4c4044a4f1b8899f443856340df302df7c1aaf8e
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-by: Ciro Santilli <ciro.santilli@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/24527
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Bobby R. Bruce <bbruce@ucdavis.edu>
Tested-by: kokoro <noreply+kokoro@google.com>