When GOMA_DISABLED is set goma will use the local compiler. Autoninja
needs to understand this in order to avoid requesting too much
parallelism.

Change-Id: Ic124893dd583a401d0d9ad7fbd27ee9b6715fcfe
Reviewed-on: https://chromium-review.googlesource.com/1015402
Commit-Queue: Bruce Dawson <brucedawson@chromium.org>
Reviewed-by: Dirk Pranke <dpranke@chromium.org>