Fix source and pip tar.gz builds on s390x systems

[cjvolzka]

Description

• Fix builds from source and pip tar.gz on s390x systems
• Revert (Fix ModuleNotFoundError: No module named 'cmake' #5195) and replace with fix from this comment from the original issue (ModuleNotFoundError: No module named 'cmake' during pip install -e . #5194)

Motivation and Context

• Building on s390x (and other environments depending on python setup) fails
  • The issue also can also appear when installing 1.16.0rc1 from TestPyPI for environments where we don't have pre-built wheels
  • Failures include not being able to find pacakges despite them being installed

    pip3 install -e . ... 
    -- Could NOT find pybind11 (missing: pybind11_DIR)
    ... 
    Traceback (most recent call last): File "/onnx/.setuptools-cmake-build/tools/protoc-gen-mypy.py", line 28, in <module>
    import google.protobuf.descriptor_pb2 as d_typed 
    
• The issue is caused by (Fix ModuleNotFoundError: No module named 'cmake' #5195) which was to fix (ModuleNotFoundError: No module named 'cmake' during pip install -e . #5194)
  • The original fix bypasses the pip venv PYTHONPATH and attempts to rely on sys.path. However without the pip venv PYTHONPATH, some modules may not be found even if they are installed.
    • For reference, the pip venv PYTHONPATH gets set to /tmp/pip-build-env-bn_o_cjc/site which contains sitecustomize.py which comes from https://github.com/pypa/pip/blob/main/tests/lib/venv.py#L171-L189
  • Instead of bypassing the pip venv PYTHONPATH, this comment from the original issue shows how to address the issue using pyproject.toml's [build-system]
• I replicated the origial issue and confirmed this fix resolves it.
• I confirmed the builds work on s390x with this fix

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 56.81%. Comparing base (b48d763) to head (b054c4f).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5984   +/-   ##
=======================================
  Coverage   56.81%   56.81%           
=======================================
  Files         506      506           
  Lines       30357    30357           
  Branches     4589     4589           
=======================================
  Hits        17246    17246           
  Misses      12283    12283           
  Partials      828      828           

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[justinchuby]

Thank you! This fix looks neat.