In addition to setting GOMA_DISABLED, this CL also sets the
RBE_remote_disabled environment variable to autoninja.

Bug: 1149386
Change-Id: I9aa8be005a9cd473b7371eadcab83d6068e0e070
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2565550Reviewed-by: Dirk Pranke <dpranke@google.com>
Commit-Queue: Michael Savigny <msavigny@google.com>