[build] bump rules_rs to 0.0.108

[titusfortner]

🔗 Related Issues

Supersedes #17929 with bump to later version to fix one bug and a patch to fix the other
Builds toward #17586

💥 What does this PR do?

• Bumps rules_rs to 0.0.108, with llvm 0.8.18 and rules_cc 0.2.22 to match the resolved graph

🔧 Implementation Notes

• need to change register_toolchains to use //... instead of :all because 0.0.108 no longer generates a root package
• The zlib snapshot patch can be dropped since it exists in 0.0.108
• rules_rust_debug_prefix_map.patch carries fix: remap assembler debug paths in Cargo build scripts hermeticbuild/rules_rust#54.

🤖 AI assistance

• AI assisted (complete below)
  • Tool(s): Claude Code (Fable 5.1)
  • What was generated: the MODULE.bazel changes, the CI log analysis, and this description
  • I reviewed all AI output and can explain the change

💡 Additional Considerations

• Follow-up: the Rust job for Windows has skipped every target as incompatible since [bazel] Swap to rules_rs for Rust build rules #17398, because the crate universe is msvc-only and the exec platform is gnullvm. Fixing that is a separate PR.
• Delete rules_rust_debug_prefix_map.patch once fix: remap assembler debug paths in Cargo build scripts hermeticbuild/rules_rust#54 lands in a pinned rules_rust

🔄 Types of changes

• Cleanup (build dependency update; no user-facing behavior change)

[qodo-code-review]

PR Summary by Qodo

Bump rules_rs to 0.0.108 and preserve hermetic Rust builds

⚙️ Configuration changes 🐞 Bug fix 🕐 10-20 Minutes

AI Description

• Bumps rules_rs to 0.0.108 and aligns LLVM and rules_cc versions.
• Applies an upstream debug-prefix fix for hermetic GCC assembly builds.
• Registers all generated Rust toolchains and removes the obsolete zlib patch.

Diagram

graph TD
  module["Bazel module"] -->|pins| rs["rules_rs 0.0.108"] -->|provides| ext["Rust extensions"] -->|generates| tc["Rust toolchains"]
  module -->|aligns| llvm["LLVM 0.8.18"]
  module -->|aligns| cc["rules_cc 0.2.22"]
  patch["Debug-prefix patch"] -->|applies to| ext

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High-Level Assessment

The following are alternative approaches to this PR:

1. Wait for the upstream rules_rust fix

• ➕ Avoids maintaining a temporary downstream patch.
• ➕ Uses an officially released implementation of the debug-prefix correction.
• ➖ Delays the rules_rs upgrade and its bundled bug fixes.
• ➖ Leaves affected GCC assembly builds failing hermeticity checks until release.

Recommendation: Proceed with the dependency bump and narrowly scoped extension patch. It adopts the rules_rs release containing the zlib fix immediately, while carrying the pending upstream debug-prefix correction in an isolated file that can be removed once hermeticbuild/rules_rust#54 is released.

Files changed (2) +28 / -13

Bug fix (1) +17 / -0

rules_rust_debug_prefix_map.patchPreserve hermetic debug paths in GCC assembly output +17/-0

Preserve hermetic debug paths in GCC assembly output

• Patches Cargo build-script C and C++ flags to include '-fdebug-prefix-map' alongside '-ffile-prefix-map'. This ensures GCC 12 and earlier forward path remapping to the assembler, preventing absolute 'DW_AT_comp_dir' values in '.S' debug information.

third_party/bazel/rules_rust_debug_prefix_map.patch

Other (1) +11 / -13

MODULE.bazelAlign Rust build dependencies and toolchain configuration +11/-13

Align Rust build dependencies and toolchain configuration

• Bumps rules_rs to 0.0.108, LLVM to 0.8.18, and rules_cc to 0.2.22 while removing the obsolete zlib snapshot override. Applies the debug-prefix patch through the rules_rust extension and registers toolchains with '//...' because the new release no longer generates a root package.

MODULE.bazel

[qodo-code-review]

Code Review by Qodo

🐞 Bugs (0) 📘 Rule violations (1) 📜 Skill insights (0)

1. A dependency refresh can erase the fix 📘 Rule violation ⚙ Maintainability

Description

rules_rust_debug_prefix_map.patch is added directly beneath the protected third_party/ area.
When that area is refreshed or replaced, the locally maintained Rust compiler fix can be overwritten
and its use from MODULE.bazel can become inconsistent.

Code

third_party/bazel/rules_rust_debug_prefix_map.patch[1]

+diff --git a/cargo/private/cargo_build_script.bzl b/cargo/private/cargo_build_script.bzl

Evidence

Compliance rule 3 prohibits direct modifications under third_party/. The cited file is newly added
by this PR at third_party/bazel/rules_rust_debug_prefix_map.patch, directly violating that path
restriction.

AGENTS.md: Do Not Modify Read-Only or Generated Repository Areas
third_party/bazel/rules_rust_debug_prefix_map.patch[1-17]

Agent prompt

The issue below was found during a code review. Follow the provided context and guidance below and implement a solution

## Issue description
The new Rust dependency patch is stored directly under the protected `third_party/` repository area.

## Issue Context
Move the patch to a repository-owned, non-generated location and update the module override to use its new label without changing the patch behavior.

## Fix Focus Areas
- third_party/bazel/rules_rust_debug_prefix_map.patch[1-17]
- MODULE.bazel[389-391]

ⓘ Copy this prompt and use it to remediate the issue with your preferred AI generation tools

---

Context sources

✅ Web pages:

  🌐 MODULE.bazel

  🌐 Bazel Central Registry

  🌐 rs/toolchains/module_extension.bzl

  +4 more

Review mode: ⚖️ Balanced: This build dependency and toolchain update changes Bazel module resolution, toolchain registration, and applies a compiler-flag patch, creating meaningful build and hermeticity risk but not enough independent logic for extended review.

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[qodo-code-review]

No code changes since the last review — review skipped