Similar to chromium side change: https://crrev.com/c/1961070.
When checkout_clang_tidy is set, we will check out clang-tidy via
clang/scripts/update.py.

The goal is to be able to run clang-tidy using Tricium.

Bug: chromium:1087565,v8:10488
Change-Id: I14ebaaca33ca20d59d9cc5e537826829608a1e6f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2242257Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68418}