sdk: get clang resources from swift toolchain

[kabiroberai]

What does this PR do?

When building the SDK, derives the clang resource dir from the installed Swift toolchain (swiftc -print-target-info) instead of clang -print-resource-dir.

Speculatively fixes #273.

How was it tested?

Validated that I can still build on Linux

AI tool usage

How much of this PR was AI-assisted? (check one)

• 0 - No AI was used to write code
• 1 - I was assisted by AI. I reviewed the finished result.
• 2 - I set the AI going and left it to it; nobody has read the result - no review, or AI review only

Summary by CodeRabbit

• Bug Fixes
  • Improved detection of the host Clang resource directory by using Swift compiler target information, helping ensure more reliable compiler setup across supported environments.

[coderabbitai]

Understand this PR’s impact

Explore downstream dependencies and potential security impact with Blast Radius.

View blast radius →

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Advanced

Run ID: 5ff888cd-8a32-4f2c-b0dc-6f84dbd78b9e

📥 Commits

Reviewing files that changed from the base of the PR and between 04c29af and 476a7bb.

📒 Files selected for processing (1)

• Sources/PackLib/DarwinSDK.swift

Included review availability: Your plan provides up to 10 included reviews per hour; 9 remain after this review.

---

📝 Walkthrough

Walkthrough

addHostClangResourceDir now runs the configured Swift compiler with -print-target-info, decodes its JSON output, and derives the host Clang resource directory from paths.runtimeResourcePath instead of querying clang.

Changes

SDK resource lookup

Layer / File(s)	Summary
Swift target information lookup Sources/PackLib/DarwinSDK.swift	addHostClangResourceDir now decodes Swift target information and appends clang to paths.runtimeResourcePath. The previous ToolRegistry lookup and clang -print-resource-dir parsing were removed.

Priority: ➖ Normal

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Bug fix · Severity of issue fixed: Medium

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	The change addresses issue #273. addHostClangResourceDir now runs the selected swiftc from BuildSettings.swiftcURL() with -print-target-info. It decodes paths.runtimeResourcePath and copies …
Out of Scope Changes check	✅ Passed	The only changed file is Sources/PackLib/DarwinSDK.swift. The change replaces PATH-based Clang discovery with selected-Swift-toolchain discovery inside SDK installation. This directly supports issue…
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely summarizes the main change: obtaining Clang resources from the Swift toolchain.

✨ Finishing Touches

📝 Generate docstrings

• Commit to this branch
• Create a new PR

🧪 Generate unit tests (beta)

• Commit to this branch
• Create a new PR

---

_{Comment @coderabbitai help to get the list of available commands.}

[kabiroberai]

• sdk: get clang resources from swift toolchain #274 👈 (View in Graphite)
• main

This stack of pull requests is managed by Graphite. Learn more about stacking.