external-builds/pytorch: add a torch-only ROCm ASAN build mode

[sa-faizal]

Stack: 2 of 2, after #7312.

For the Phase 2-only review diff, compare draft/asan-wheels-phase1-rocm...draft/asan-wheels-phase2-pytorch.

Summary

Add the integrated Phase 2 production-builder mode for a torch-only ROCm ASAN wheel built from the isolated Phase 1 package set:

• validate the local manifest, exact coherent ROCm ASAN version, bootstrap frontend, and single gfx942:xnack+ target;
• install the SDK offline with --no-index, --no-build-isolation, exact versioning, and the selector's device extra;
• select packaged ROCm Clang, bitcode, and the shared ASAN runtime and configure shared-ASAN/frame-pointer flags;
• disable CMake's optional module scanner while preserving caller CMAKE_ARGS;
• derive a collision-resistant Torch suffix from the selected ROCm candidate;
• keep the prebuilt ASAN AOTriton path enabled without building a separate Triton wheel; and
• scope LD_PRELOAD to the post-install Torch sanity subprocess only.

ASAN mode opts into the generic portable-RPATH contract from #7210; its parser/archive-gate implementation is deliberately not duplicated here.

Why this is a draft

• the reusable builder still contains pilot policy for ROCm 10.1 and gfx942:xnack+ that should move into workflow configuration;
• the final fat wheel must be rebuilt after the compiler-rt and portable-RPATH dependencies land;
• the independent kpack PEP 376 RECORD correction in ROCm/rocm-systems must land before the final split; and
• strict offline GPU validation must replace the historical diagnostic baseline before publication.

Real-input evidence

The prototype consumed the Phase 1 10.1.0+asan.20260807 index and a HIPified PyTorch checkout based on dcf02e51371deb3050899643462349c1941e8979.

• the full 3,830-edge Torch build completed and produced a 643 MiB fat wheel;
• the isolated import sanity check reported 2.14.0a0+rocm10.1.asan.20260807;
• corrected split host/device wheels passed ZIP CRC, full PEP 376 RECORD, reciprocal pin, kpack, and ASAN-linkage validation;
• clean CPython 3.12 offline installation and plain Torch import passed;
• the GPU smoke reached the known pre-fix compiler-rt null-PC initialization failure, so the preserved artifacts are diagnostic evidence, not publishable outputs.

No local runner, wheel, dependency wheelhouse, generated AOTriton images, PyTorch HIPIFY output, submodule pointer, or validation artifact is included.

Tests

20 focused ASAN production-builder tests passed
python -m py_compile: pass
git diff --check: pass

The three portable-RPATH tests from the integrated prototype were excluded because #7210 owns that implementation and its focused coverage.

Dependencies and final acceptance

• packaging: add ROCm ASAN wheel production #7312 — coherent ROCm ASAN package/index input
• external-builds/pytorch: validate portable wheel RPATHs #7210 — portable Torch RPATH activation and archive gate
• cmake: add opt-in portable RPATHs for TheRock ROCm wheels pytorch#3549 — portable PyTorch CMake RPATH policy
• [ASan][AMDGPU] Retry HSA resolution after late HIP load llvm-project#3827 — late-HSA compiler-rt initialization fix
• independent ROCm/rocm-systems kpack RECORD fix

After those dependencies land, rebuild rather than patch the preserved wheels and require zero absolute RPATH/RUNPATH components, strict offline installation, successful gfx942 tensor execution (1240.0), and zero downgraded ASAN findings.

[therock-pr-bot]

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[ScottTodd]

Stack: 2 of 2, after #7312.

For the Phase 2-only review diff, compare draft/asan-wheels-phase1-rocm...draft/asan-wheels-phase2-pytorch.

You can stack your PR either with https://docs.github.com/en/pull-requests/how-tos/stacked-pull-requests or by changing the base branch for this PR to that other branch, fyi. Both require creating branches in the shared repository, which is what we recommend for AMD employees anyways: https://github.com/ROCm/TheRock/blob/main/CONTRIBUTING.md#branch-creation-policy.