gem5 supports Tarmac trace generation for Arm simulations, but there are no examples of how to use this feature. This patch adds a `--tarmac-gen` option to three of the simple Arm configs. Tarmac generation is useful for out-of-the-box users, and this patch also provides an example of how to use the Tarmac generation feature. Change-Id: I0d3c523b5c0bb6d94de93bc502e4451622fb635d Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/69684 Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com> Maintainer: Giacomo Travaglini <giacomo.travaglini@arm.com> Tested-by: kokoro <noreply+kokoro@google.com>