This changes adds all of the workflows that will be run as we move to using GitHub. It includes our compiler tests, our nightly runs, and the continuous integration tests to be run on every pull request. Change-Id: I54c79aca7c0603337bd9fca443a0e2ffef603b0e Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/71298 Reviewed-by: Bobby Bruce <bbruce@ucdavis.edu> Tested-by: kokoro <noreply+kokoro@google.com> Maintainer: Bobby Bruce <bbruce@ucdavis.edu>