util: Add config files for crosstool-ng toolchains.

util: Add config files for crosstool-ng toolchains.

There is one for each arch gem5 supports, except RISCV which is not
supported by crosstool-ng at the moment. All configs are for Linux, also
because that's what crosstool-ng tends to support.

Change-Id: I898a9e8c7b144c3d690c232fd4fb20ede5430def
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/27758
Tested-by: Gem5 Cloud Project GCB service account <345032938727@cloudbuild.gserviceaccount.com>
Reviewed-by: Ciro Santilli <ciro.santilli@arm.com>
Maintainer: Gabe Black <gabeblack@google.com>