Fix macOS arm64 build compatibility with Xcode compiler toolchain clang 17

[czgdp1807]

Problem

Building tfx-bsl on macOS arm64 with Xcode Command Line Tools (clang 17) fails due to several incompatibilities:

1. Linker error: ThinLTO assumes Apple's libLTO.dylib, causing failures with conda-provided compilers
2. zlib compilation: Macro conflicts between zlib 1.2.11 and modern macOS SDK headers
3. Module symbols: Python 2-era extension symbols cause linker failures on Python 3
4. Dependency mismatch: tensorflow-serving-api version drift from tensorflow 2.17

Solution

This PR addresses all macOS-specific build failures:

Changes

.bazelrc

• Disable ThinLTO on macOS/macOS arm64 to avoid linker errors with conda compilers
• Define HAVE_UNISTD_H=1 for zlib compatibility with modern macOS headers

WORKSPACE

• Update zlib to version 1.3.1 (from implicit 1.2.11)
• Define explicit http_archive for zlib before tensorflow dependency loads it
• Prevents fdopen macro conflicts with macOS SDK _stdio.h

setup.py

• Pin tensorflow-serving-api to ==2.17.1
• Updated all selectors: default, nightly, and git_master branches
• Ensures consistent protobuf/grpc versions across all build configurations

tfx_bsl/build_macros.bzl

• Remove Python 2 module initialization symbols (init_*, init*)
• Keep only PyInit_<module> for Python 3 compatibility
• Fixes undefined symbol errors during extension module linking

Testing

Verified on: macOS arm64, Python 3.12, Bazel 6.5.0

• Build completes without compiler or linker errors
• tfx_bsl_extension.so correctly links
• Package installs via pip install -e .

Impact

• Enables macOS arm64 builds with conda environments
• No changes to Linux/Windows builds (macos-specific flags)
• Maintains Python 3.9+ compatibility
• Drops Python 2 support (already EOL)

Related Issues

Fixes compilation errors on macOS when using conda's clang/clang++ toolchain instead of Apple's Xcode developer tools.