The Skia bots have been unable to roll ANGLE since parallel compile landed in
ANGLE.  Speculatively disable parallel compile using a workaround.
Failed roll: https://skia-review.googlesource.com/c/skia/+/184705

Also seen instability on Linux, Mac and Windows in 922936.

BUG=922936
BUG=849576

Change-Id: I7116b3f6541425135984c52a8077bdb98d961784
Reviewed-on: https://chromium-review.googlesource.com/c/1415729Reviewed-by: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Geoff Lang <geofflang@chromium.org>