Copybara import of the project:

[copybara-service]

Copybara import of the project:

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f303d03 by Lukasz Anforowicz lukasza@google.com:

Bazel build of rs_bindings_from_cc:cc_ir.

The primary change and the goal of this commit is enabling building of
the cc_ir target and covering this target via GitHub CI/CQ (see the
one line change in rust.yml). This primary change is supported by
teaching Bazel how to build LLVM/Clang from sources:

• Migrating LLVM dependency to Bzlmod and replacing the old
  WORKSPACE-based loader with a new module extension
  (llvm_extension.bzl) that downloads LLVM source and configures
  host dependencies (zlib, libxml2, zstd).
• Using Clang/LLVM dependency locked to a specific Git commit hash
  specified in MODULE.bazel: llvm_ext.configure(commit = "...").
  • We use Renovate (via .github/renovate.json) to automate rolls -
    it will open a PR to update the commit hash as/when needed.
  • Note that MODULE.bazel asks for Clang/LLVM 22.1.0 to be used
    as a compiler (i.e. the llvm_ext.configure compiler is not
    used during Bazel builds - it only becomes part of the
    rs_bindings_from_cc tool).
• The Clang/LLVM dependency needs to be patched to account for
  unsupported platforms. This kind of patching mimics how other OSS
  projects work with Clang/LLVM:
  • https://github.com/google/xls/blob/64bf93a3963dc6fd55b749e457e3345c91a5091f/dependency_support/llvm/platforms_config.patch
  • https://github.com/carbon-language/carbon-lang/blob/f58de06c0dbd506573620d8f2873923a8697c925/bazel/llvm_project/0011_Temporarily_remove_reference_to_hermetic_toolchain.patch

FUTURE_COPYBARA_INTEGRATE_REVIEW=#1757 from anforowicz:clang-dependency f303d03