[Bug Report] HSACOError & FileNotFoundError when compiling Triton kernel on Hygon BW1000 HCU

Environment Information
- Image: flagtree-hcu3.6-py310-torch2.4.1-ubuntu22.04:202604-base
- Hardware: Hygon BW1000 (arch: gfx936)
- GPU Count: 8
- Installation Method: Source-free installation following documents/install_hcu_cn.md (Section 2.1)
- Component Versions:
- flagtree: 0.6.0+hcu3.6
- triton: 3.6.0
- TRITON_HIP_CLANG_PATH: /opt/dtk/dcc/bin/clang (clang-17.0.0 from DTK driverruntime branch)
Problem Description

Reproduction Steps
# Launch container
docker run ... flagtree-hcu3.6-py310-torch2.4.1-ubuntu22.04:202604-base

# Inside container (pip install can be skipped as the image is pre-installed)
pip install flagtree===0.6.0+hcu3.6
python3 python/tutorials/01-vector-add.py
Error Log (Key Part)
File ".../triton/backends/hcu/compiler_hcu.py", line 756, in make_amdgcn
with open(asm_file, "r") as fd_out:
FileNotFoundError: [Errno 2] No such file or directory: '/tmp/tmpXXXX.amdgcn'
...
HSACOError: HSACO error: File operation failed: ...

Clang stderr output (unknown arguments):
clang (LLVM option parsing): Unknown command line argument '-check-valu-data-forward-hazards=0'
clang (LLVM option parsing): Unknown command line argument '-disable-cluster-lds-memops=true'

Root Cause Analysis
1. The make_amdgcn function of HCU backend passes several HCU-proprietary LLVM flags via _get_clang_args when compiling LLVM IR (.ll) to amdgcn assembly (.amdgcn). These flags are only supported by Hygon-customized LLVM, not standard upstream clang.
2. The path_to_rocm_clang() resolves to /opt/dtk/dcc/bin/clang (standard clang-17), which cannot recognize the HCU-specific flags, leading to compilation failure and missing .amdgcn output file. This triggers FileNotFoundError and is finally wrapped into HSACOError.
3. The default expected clang path for path_to_rocm_clang() is /opt/dtk/aillvm/bin/clang-18 (aillvm branch), which does not exist in the current image.
4. The built-in hcu-llvm22 (~/.flagtree/hcu/hcu-llvm22-xxx) only provides backend tools (llc/opt/lld/mlir-opt) without clang frontend. Itsllc also lacks support for the above HCU-specific flags and is only used for build-time processing, not runtime kernel compilation.

Key Verification Evidence
1. Standard clang-17 has no HCU proprietary flag support:
strings /opt/dtk/dcc/bin/clang-17 | grep -c "check-valu-data-forward-hazards"
# Output: 0
2. Built-in hcu-llvm22 llc lacks all related HCU flags:
llc --help-hidden | grep -E "check-valu-data-forward-hazards|disable-cluster-lds-memops|hcu-pre-emit-load-store-opt|support-768-vgprs"
# No output
3. Expected aillvm clang directory missing:
ls /opt/dtk/aillvm/bin/clang-18
# ls: cannot access '/opt/dtk/aillvm/bin/clang-18': No such file or directory

Questions for Maintainers
- Is the 202604-base image missing the Hygon-customized clang (aillvm clang-18) required for runtime Triton kernel compilation?
- What is the correct compiler toolchain configuration for running Triton HCU kernels on the current official image?
- Is there a temporary workaround to bypass the unsupported hardcoded HCU compilation flags for standard clang?
- Will the official base image be updated to include the complete customized LLVM/clang toolchain for HCU backend?

Start with triton/backends/hcu/compiler_hcu.py, especially make_amdgcn and path_to_rocm_clang, then reproduce python3 python/tutorials/01-vector-add.py in the stated container. Compare the configured clang path and supported flags with the error output; done means Triton HCU kernel compilation completes without the missing .amdgcn or HSACOError.

Written by the indexing model from the issue text.