Add clang_tidy_tool.py to fetch, build, and invoke clang-tidy

Bug: 936989
Change-Id: I283cbb9f87e912c8094872a70c6abc193659cbe2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1497198
Reviewed-by: Nico Weber <[email protected]>
Commit-Queue: Daniel McArdle <[email protected]>
Cr-Commit-Position: refs/heads/master@{#638591}
diff --git a/docs/clang_static_analyzer.md b/docs/clang_static_analyzer.md
index b63cd593..8935ffa 100644
--- a/docs/clang_static_analyzer.md
+++ b/docs/clang_static_analyzer.md
@@ -29,6 +29,10 @@
 * [Linux buildbot logs](https://ci.chromium.org/p/chromium/builders/luci.chromium.ci/Linux%20Clang%20Analyzer)
 
 ## Enabling static analysis
+
+*Warning:* `use_clang_static_analyzer` is deprecated, but the static analyzer can
+still be invoked with [clang-tidy](clang_tidy.md).
+
 To get static analysis running for your build, add the following flag to your GN
 args.