Allow clang-tidy to be checked out via DEPS

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}

DEPS

@@ -24,6 +24,8 @@ vars = {
 
   'checkout_instrumented_libraries': False,
   'checkout_ittapi': False,
+  # Fetch clang-tidy into the same bin/ directory as our clang binary.
+  'checkout_clang_tidy': False,
   'chromium_url': 'https://chromium.googlesource.com',
   'android_url': 'https://android.googlesource.com',
   'download_gcmole': False,
@@ -485,6 +487,13 @@ hooks = [
     'condition': 'host_os != "aix"',
     'action': ['python', 'v8/tools/clang/scripts/update.py'],
   },
+  {
+    'name': 'clang_tidy',
+    'pattern': '.',
+    'condition': 'checkout_clang_tidy',
+    'action': ['python', 'v8/tools/clang/scripts/update.py',
+               '--package=clang-tidy'],
+  },
   {
     # Update LASTCHANGE.
     'name': 'lastchange',