[CI] Minor CMake refactoring

[fheinecke]

Description

This fixes a couple of minor CMake bugs, and slightly simplifies NCCL dependency resolution.

Type of change

• Documentation change (change only to the documentation, either a fix or a new content)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Infra/Build change
• Code refactoring

Changes

Please list the changes introduced in this PR:

• 28fe8ee: NCCL header location is now resolved once instead of two separate places with different resolution hints.
• b6303b8: Python site-packages/nvidia/nccl is now searched for NCCL headers, making it easier to resolve them when installing NCCL via nvidia-nccl-cu{12,13} wheels.
• 30d92a7: The TE version linker script is now only provided when TE is linked, rather than every time the C++ or CUDA compiler is executed (compiler detection, compilation, etc).

Checklist:

• I have read and followed the contributing guidelines
• The functionality is complete
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[fheinecke]

/te-ci

[fheinecke]

/te-ci

[greptile-apps]

Greptile Summary

This PR performs three targeted CMake improvements in transformer_engine/common/CMakeLists.txt: it consolidates duplicate NCCL header discovery into a single find_path call at the top level (adding Python site-packages as a search hint), renames the helper function to get_nccl_version to reflect its new narrower role, and moves the linker version-script from global CMAKE_CXX_FLAGS/CMAKE_CUDA_FLAGS to a target_link_options(PRIVATE ...) on the transformer_engine target.

• The version-script change is a genuine bug fix: the old global flag was injected into every compiler invocation (compiler detection, try_compile, and subproject targets like nvshmemapi), which could cause spurious link failures. Scoping it with target_link_options is the correct CMake idiom.
• The NCCL consolidation drops the internal find_path from inside the old find_nccl_version function and the one inside the NVTE_WITH_NCCL_EP conditional, replacing both with a single top-level find_path ... REQUIRED call. A side-effect is that nccl.h is now unconditionally required at configure time, even when NVTE_WITH_NCCL_EP=OFF and NVTE_WITH_CUBLASMP=OFF; in practice this is fine since the always-compiled comm_gemm_overlap sources reference NCCL symbols.

Confidence Score: 5/5

Safe to merge. All three changes are scoped, correct, and reduce unintended side-effects of the previous implementation.

The linker-script fix removes a real CMake anti-pattern where a link-only flag was injected into every compiler invocation project-wide. The NCCL consolidation is functionally equivalent for the existing call sites and adds a useful new search path. No existing override mechanisms (e.g. -DNCCL_INCLUDE_DIR) are broken.

No files require special attention.

Important Files Changed

Filename	Overview
transformer_engine/common/CMakeLists.txt	Three clean improvements: linker version-script scoped to the transformer_engine target via target_link_options; NCCL header discovery consolidated into one top-level find_path with an added Python site-packages hint; get_nccl_version helper simplified to not do its own path search. No logic regressions observed.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[CMake configure start] --> B[find_path NCCL_INCLUDE_DIR\nHINTS: Python site-packages,\n/opt/nvidia/nccl, /usr/local/nccl\nREQUIRED]
    B -->|found| C[get_nccl_version\nNCCL_VERSION]
    B -->|not found| FAIL1[FATAL_ERROR]

    C --> D[add_library transformer_engine SHARED]
    D --> E[target_link_options PRIVATE\nLINKER:--version-script=\nlibtransformer_engine.version]
    D --> F[target_include_directories PRIVATE\nNCCL_INCLUDE_DIR]

    G{NVTE_WITH_CUBLASMP?} -->|ON| H[Check NCCL_VERSION >= 2.30.0\nusing already-resolved NCCL_INCLUDE_DIR]
    G -->|OFF| I[skip]

    J{NVTE_WITH_NCCL_EP?} -->|ON| K[find NCCL_EP headers & lib\ntarget_include_directories NCCL_EP_INCLUDE_DIR]
    J -->|OFF| L[compile stub ep_api.cpp]

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