[thiagogenez]

On Intel macOS 26, brew doctor reports CLT 26.6 as outdated even though it is the latest compatible release. The check requires clang 2100.3.34.2, but CLT 26.6 provides 2100.1.1.101.

Use the CLT 26.6 threshold on Intel macOS 26. The existing physical_cpu_arm64? helper keeps the newer threshold on Apple Silicon, including under Rosetta. macOS 27 keeps its current threshold, and older Intel CLTs still trigger the warning.

Fixes #24041.

To reproduce on an Intel Mac running macOS 26 with CLT 26.6 installed:

1. Run brew doctor check_clt_up_to_date before applying the patch.
2. Apply the patch and run the same command. The warning A newer Command Line Tools release is available. disappears.

Validation:

• Verified the threshold directly from Apple's standalone CLT 26.6 Universal executables package, identified by Apple's distribution metadata. pkgutil --check-signature reported signed Apple Software; the extracted PackageInfo identifies com.apple.pkg.CLTools_Executables version 26.6.0.0.1781586589. Running the extracted clang --version on arm64 and via arch -x86_64 returned clang-2100.1.1.101 in both cases. The package was extracted to a temporary directory, not installed.
• Regression tests cover Intel CLT 26.6, older Intel CLTs and Apple Silicon both natively and under Rosetta. The Intel and Rosetta regression examples failed before their fixes and passed afterwards using the same targets. All six focused examples passed: ./bin/brew tests --only=os/mac/xcode:54,os/mac/xcode:62,os/mac/xcode:76,os/mac/xcode:82,os/mac/xcode:88.
• ./bin/brew lgtm --online passed: type checking, style and all 12 examples in the affected spec on the development machine.

I also checked the threshold before and after the patch on an Intel MacBook running Ventura 13.6, in a separate clone. This command simulates macOS 26.7 inside the Ruby process and uses the Mac's real CPU:

HOMEBREW_NO_AUTO_UPDATE=1 ./bin/brew ruby -- -e 'require "os/mac/xcode"; MacOS.full_version = "26.7"; puts MacOS::CLT.latest_clang_version'

Revision	Reported Clang threshold
Before: 14c54f7c76	2100.3.34.2
After: patched branch	2100.1.1.101

Note

My Intel Mac runs Ventura 13.6, and I need to keep its macOS and Homebrew installation unchanged. I tested in a separate clone, simulating macOS 26.7 within the Ruby process. RSpec was blocked by native gem compilation failures. I have not tested the full setup on Intel with macOS 26 and CLT 26.6 installed.

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• I did not use AI/LLM to create this PR, or I disclosed the tool/model below and reviewed its output; I did not attribute commits to AI and will answer maintainer questions and review comments myself without AI/LLM.

I used OpenAI Codex (GPT-6) to investigate the issue, draft the patch, tests and this description, verify the Apple package and run the automated checks. I ran the Intel before/after check and reviewed the code and this description.

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[MikeMcQuaid]

Thanks!