commit 6a2f5d58057bec0f06391661aabeb613347bcae7
author Lukasz Anforowicz <lukasza@chromium.org> Tue Jul 19 23:24:08 2022
committer Chromium LUCI CQ <chromium-scoped@luci-project-accounts.iam.gserviceaccount.com> Tue Jul 19 23:24:08 2022
tree 08f3ceef89d3c903a4128a34dad16248cd4fd228
parent 56c26c57075281674f3ccf887db203b972ec90b8

[rust] Support for DEPS-ing in Bazel (only for build_crubit.py).

This CL adds support for DEPS-ing in a Bazel binary, because Bazel is
needed by //tools/rust/build_crubit.py. This means that Bazel is only
needed ...:

- ... for Chromium Rust Experiments project (the new entry will
  have no impact on other Chromium engineers unless they opt in by
  setting `checkout_bazel`).

- ... when building Rust toolchain (the Rust compiler, and in
  the future Crubit and/or Autocxx tools).  In other words this CL does
  not mean that the regular Chromium build will use Bazel for anything.

The CIPD packages with the Bazel binary are configured via
//3pp/bazel_bootstrap/3pp.pb in the Chromium infra repo.  Based on the
discussion at chrome-rust-experiemnts@[1] depending on the latest
*bootstrap* version seems ok, because "Bazel can only be built using
itself [...] so we do need to trust the prebuilt binaries to some
extent".  The latest package [2] contains Bazel 5.2.0.

The decision to build Rust toolchain on Clang-related bots has been
captured in an earlier design doc [3].  A recent update to the doc
explains why we will use Bazel to build Crubit (and why other
alternatives would not work as well).  A separate follow-up CL will
configure these bots to set `checkout_bazel` in their `.gclient` config
file.

[1] https://groups.google.com/a/google.com/g/chrome-rust-experiments/c/skuOvBe4B1c/m/yLCqXD2EAgAJ
[2] https://chrome-infra-packages.appspot.com/p/infra/3pp/tools/bazel_bootstrap/linux-amd64/+/
[3] https://docs.google.com/document/d/1ypIjF_7gZ1h3ydewUYo_a75VtBJ_Q5Uauu4WqHTce9c/edit?usp=sharing&resourcekey=0-uZimEpzBtaWyDEL-53vijQ

Bug: 1329611
Change-Id: Ibf8bcb6d0bbd0d471c3e3649287bdd20da5f1a68
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3763581
Reviewed-by: Nico Weber <thakis@chromium.org>
Commit-Queue: Łukasz Anforowicz <lukasza@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1025999}