[AMD] Improve ld.lld detection for ROCm SDK / ROCM_PATH installs

[adityas-amd]

Backports a small path_to_rocm_lld() change to release/internal/3.3.x. On main and release/3.5.x this code path was already removed by triton-lang#7548 ([AMD] Use lld library API for linking), so this PR is targeted only at the still-shipping branches that PyTorch 2.7.x consumes via pytorch-triton-rocm
fixes: ROCm/TheRock#2006 .

What changes

HIPBackend.path_to_rocm_lld() now also probes:

• $ROCM_PATH/llvm/bin/ld.lld when ROCM_PATH is set,
• $(rocm-sdk path --root)/llvm/bin/ld.lld when rocm-sdk is on PATH (TheRock SDK case),
• shutil.which("ld.lld") as a final fallback.

The error message now lists every probed location.

Why

Landing here on release/internal/3.3.x (where pytorch-triton-rocm is built) per @antiagainst's review on triton-lang#10387. Upstream main already drops this
path via triton-lang#7548.

On TheRock SDK installs (Python wheel layout, no /opt/rocm), Triton fails to compile any kernel unless TRITON_HIP_LLD_PATH is exported manually. The failure fires from HIPBackend.hash() via torch.utils._triton.triton_hash_with_backend(), which Inductor calls whenever it codegens a Triton kernel — so torch.compile and aoti_compile_and_package are unusable without the workaround.

Reproduced locally with torch==2.7.1 + pytorch-triton-rocm==3.3.1 on a TheRock-only host (no /opt/rocm; ld.lld only present under $(rocm-sdk path --root)/llvm/bin/ld.lld). Original ROCm/triton draft was #908 (will close in favor of this one).

See ROCm/TheRock#2006 for the full traceback.

New contributor declaration

• I am not making a trivial change, such as fixing a typo in a comment.

• I have written a PR description following these
  rules.

• I have run pre-commit run --from-ref origin/main --to-ref HEAD.

• Select one of the following.

  • I have added tests.
    • /test for lit tests
    • /unittest for C++ tests
    • /python/test for end-to-end tests
  • This PR does not need a test because the change is environment-dependent filesystem probing of the ROCm linker path. Exercising the new branches requires either a TheRock SDK install (so rocm-sdk path --root resolves to a real directory containing llvm/bin/ld.lld) or ROCM_PATH pointing at a populated ROCm install, neither of which is available in the upstream CI environment. The pre-existing fallbacks (TRITON_HIP_LLD_PATH, bundled <triton>/llvm/bin/ld.lld, /opt/rocm/llvm/bin/ld.lld, /usr/bin/ld.lld) are unchanged and remain exercised by existing builds.

• Select one of the following.

  • I have not added any lit tests.
  • The lit tests I have added follow these best practices,
    including the "tests should be minimal" section. (Usually running Python code
    and using the instructions it generates is not minimal.)

[adityas-amd]

Landing on ROCm/triton:release/internal/3.3.x per review - see triton-lang#10387. Approval carried over