ci(build): pin MSVC toolset to 14.44 for Windows CUDA portable build

[ingim]

Root cause

The portable / x86_64-windows-cuda job broke on runner image drift, not code — the same job was green on the last run. The windows-large-x64 runner drifted to Visual Studio 18, which now ships two MSVC toolsets: 14.44.35207 (MSVC 19.44) and 14.51.36231 (MSVC 19.51). TheMrMilchmann/setup-msvc-dev with no toolset pin activates the newest (14.51), which the pinned CUDA 12.9.1 toolkit does not support:

• nvcc's host_config.h version gate rejects it during CMake's CUDA compiler probe — C1189: unsupported Microsoft Visual Studio version.
• Forcing past that gate with -allow-unsupported-compiler just moves the failure downstream: nvcc's front-end crashes — nvcc error : 'cudafe++' died with status 0xC0000005 (ACCESS_VIOLATION). So the newer MSVC is genuinely incompatible with CUDA 12.9, which is exactly why the gate exists.

Fix

Pin the VC++ toolset to 14.44 (MSVC 19.44) in the Windows CUDA step. 14.44 ships on the current image (confirmed via the run's vcvars dump) and is within CUDA 12.9.1's supported host-compiler range, so nvcc's probe and the ggml-cuda build both succeed. The -allow-unsupported-compiler approach was evaluated and dropped (it segfaults cudafe++).

uses: TheMrMilchmann/setup-msvc-dev@v4.0.0
with:
  arch: x64
  toolset: "14.44"

Verification

Green test run: https://github.com/pie-project/pie/actions/runs/28537465006 — portable / x86_64-windows-cuda built and packaged pie-x86_64-windows-cuda.zip end-to-end in 13m20s (cargo build → package → upload). Tested with a windows-cuda-only matrix + throwaway tag; this PR restores the full matrix and carries only the toolset pin.

Notes

• Code was unchanged since the last green build — pure toolchain drift.
• Re-evaluate the pin on a future CUDA-toolkit bump or if the runner image drops 14.44 (at which point bumping the CUDA toolkit to one supporting the newer MSVC becomes the alternative).

Summary by CodeRabbit

• Bug Fixes
  • Improved Windows CUDA build reliability by using a compatible compiler toolset during portable build jobs.
  • Reduced the chance of build failures caused by toolchain mismatch checks.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 6559f655-ff27-4ecd-80ed-4ef48502b549

📥 Commits

Reviewing files that changed from the base of the PR and between 496a124 and 80d53cf.

📒 Files selected for processing (1)

• .github/workflows/build.yml

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Walkthrough

This change updates the GitHub Actions workflow for the Windows CUDA portable build leg, pinning the MSVC toolset version to "14.44" in the setup-msvc-dev step, along with added explanatory comments.

Changes

CI Windows CUDA Toolchain Pin

Layer / File(s)	Summary
Pin MSVC toolset version .github/workflows/build.yml	The Windows CUDA build leg's setup-msvc-dev step now pins toolset: "14.44" in addition to arch: x64, with comments explaining the pin avoids MSVC/CUDA 12.9.1 compiler probing incompatibilities.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately summarizes the main change: pinning MSVC toolset 14.44 for the Windows CUDA portable build.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch ci/win-cuda-msvc-fix

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