This defines V8_JITLESS_MODE if the v8_enable_lite_mode build-time
option is enabled. Jitless mode will thus be tested by existing lite
bots.

The build-time option for jitless mode will only be needed temporarily
and is expected to be removed again in the near future.

Bug: v8:7777
Change-Id: I556ba5069dbd0810a6d7376601d8f7d498fef8c9
Reviewed-on: https://chromium-review.googlesource.com/c/1387499Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58433}