The compiler dispatcher is not being used yet by Ignition, so we shouldn't
enable it when enabling Ignition + TurboFan by default.

Change-Id: I2806608ba95080df3538ef66373165107ac3beb6
Reviewed-on: https://chromium-review.googlesource.com/451279
Commit-Queue: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Jochen Eisinger <jochen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#43677}