build: refresh InfiniCCL environment exports

[Ziminli]

Summary

This PR updates scripts/build.sh to export both INFINICCL_ROOT and InfiniCCL_ROOT in ~/.bashrc. The new InfiniCCL_ROOT export matches CMake's package-root variable convention for find_package(InfiniCCL), avoiding reliance on the all-uppercase INFINICCL_ROOT variable that can trigger CMP0144 developer warnings in downstream CMake projects.

Changes

• CMake Package-Root Compatibility

  • Add the InfiniCCL_ROOT export to ~/.bashrc so downstream find_package(InfiniCCL) usage has a CMake-compatible package-root variable;
  • Avoid depending only on the all-uppercase INFINICCL_ROOT, which CMake may ignore for find_package(InfiniCCL) under CMP0144 compatibility behavior.

• Environment Setup

  • Add a helper to update existing ~/.bashrc exports or append them when missing;
  • Refresh both root exports from the current checkout path;
  • Move .bashrc updates out of the current-session PATH check so root variables are maintained even when PATH already contains the install bin directory.

Platform and Backend Affected

Platform

• N/A- CPU
• N/A- NVIDIA GPU
• N/A- Iluvatar GPU
• N/A- MetaX GPU
• N/A- Moore Threads GPU
• N/A- Cambricon MLU

Backend

• N/A- OpenMPI
• N/A- MPICH

Performance Impact

• No performance impact
• Performance improved
• Performance regression possible

N/A. This PR only changes build/install environment setup in scripts/build.sh.

Known Issues & Future Work

• N/A.

Test Results

Test Involved Platform

• CPU
• NVIDIA GPU
• Iluvatar GPU
• MetaX GPU
• Moore Threads GPU
• Cambricon MLU

Test Involved Backend

• OpenMPI
• MPICH

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Checklist

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Scope and Design

• Changes are minimal — no unrelated modifications were introduced (CONTRIBUTING.md §Code/General).
• No dead code, commented-out blocks, debug prints, printf/std::cout/print(...) left behind, or TODO without an owner and issue link.
• No unrelated formatting churn that would obscure the diff.
• N/A- Public API changes (if any) are intentional, documented, and reflected in affected callers/tests.

General Code Hygiene

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• Comments and error messages are complete sentences — capitalized first letter, terminal punctuation — unless the language/framework convention says otherwise (CONTRIBUTING.md §Code/General; §Python).

C++ Specific (if C++ files changed)

• N/A- Code follows the Google C++ Style Guide strictly.
• N/A- clang-format (version 16, per .github/workflows/clang-format.yml) has been run against all modified applicable files; the diff is clean.
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• N/A- Exactly one blank line between classes, between classes and functions, and between functions (CONTRIBUTING.md §C++).
• N/A- Exactly one blank line between members (functions and variables) within a class (CONTRIBUTING.md §C++).
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Python Specific (if Python files changed)

• N/A- Code is PEP 8 compliant; ruff check passes cleanly on CI (see .github/workflows/ruff.yml).
• N/A- ruff format --check passes cleanly — if not, run ruff format and commit the result.
• N/A- Comments are complete English sentences, starting with a capital letter and ending with punctuation; Markdown backticks are used for code references (CONTRIBUTING.md §Python).
• N/A- Framework-specific conventions (e.g. lowercase pytest.skip messages without terminal period) are honored where applicable (CONTRIBUTING.md §Python).
• N/A- No blank line between the function signature and the body when there is no docstring or comment (CONTRIBUTING.md §Python).
• N/A- A blank line is present before and after if, for, and similar control-flow statements (CONTRIBUTING.md §Python).
• N/A- A blank line appears before each return, except when it directly follows a control-flow statement (CONTRIBUTING.md §Python).
• N/A- Docstrings (if any) follow PEP 257 (CONTRIBUTING.md §Python).
• N/A- Type hints are added / kept consistent with the surrounding code.

Testing

• All applicable example programs have been built and tested successfully on at least one supported heterogeneous cluster setup.

Build, CI, and Tooling

• N/A- New backends or devices have been added to auto-detection in CMakeLists.txt under if(AUTO_DETECT_DEVICES) or to if(AUTO_DETECT_BACKENDS) if applicable.
• Both CI workflows (clang-format.yml, ruff.yml) are green locally (or expected to be green on CI).

Documentation

• N/A- README.md, CONTRIBUTING.md, or inline docs updated when behavior, build flags, or developer workflow changed.
• N/A- Any user-visible breaking change is called out explicitly under "Summary" and in the commit/PR title with a ! or BREAKING CHANGE: footer.

Security and Safety

• No secrets, access tokens, internal URLs, customer data, or personal hardware identifiers have been committed.
• N/A- Third-party code is license-compatible and attributed.
• No unsafe pointer arithmetic, uninitialized reads, or missing bounds checks were introduced.