wheel: strip non-extern symbols on macOS and Linux

[Grantim]

Summary

The macOS pip wheel ships every Mach-O binary with its __LINKEDIT segment intact. On mrmeshpy.so (124.6 MB) __LINKEDIT is 82.8 MB — 67% of the file; libopenvdb.dylib shows the same: 49 MB of 68.8 MB. The macOS build has no strip step; the Linux build has auditwheel repair but doesn't pass --strip, so the 99 bundled libs in meshlib.libs/ retain ~15 MB of .symtab/.strtab/.debug_* they don't need at runtime.

This PR adds the missing strip step on both platforms:

• macOS — strip -x between delocate-path and delocate-wheel in scripts/wheel/build_wheel.py. -x removes only local symbols; externs that dyld binds (PyInit_*, library entrypoints) stay intact, so dynamic loading is unaffected. chmod +w first because delocate copies brew dylibs preserving their 0444 mode. delocate-wheel runs after the strip and re-validates / re-signs.
• Linux — --strip flag on auditwheel repair. auditwheel runs strip on each bundled library during the repair step.
• Windows — no change. PE files don't carry the equivalent symbol payload; PDBs are external and not bundled by delvewheel.

Expected savings from analysis of v3.1.2.192 wheels:

• macOS .whl (compressed): roughly −30 MB per wheel × 2 architectures
  • mrmeshpy.so 124.6 → ~50 MB uncompressed
  • libopenvdb.dylib 68.8 → ~25 MB uncompressed
• Linux .whl (compressed): roughly −3-5 MB per wheel × 2 architectures
  • 15 MB of strippable bytes across 99 bundled .so files (mostly .strtab which compresses well, hence the modest net savings)

Test plan

CI under the test-pip-build label produces all 4 wheel artifacts; size delta is visible in the workflow summary.

• CI builds all 5 pip-build matrices green (macos x86, macos arm64, manylinux x86_64, manylinux aarch64, win amd64)
• Compare each platform's artifact size to baseline (current master) — confirm ~30 MB drop on macOS, ~3-5 MB on Linux, ~0 on Windows
• pip install the macOS arm64 wheel in a fresh venv, run import meshlib.mrmeshpy; meshlib.mrmeshpy.makeCube() — should succeed (catches any extern accidentally trimmed)
• Same for Linux x86_64 wheel
• Spot-check lief.parse(...).segments on a stripped Mach-O: __LINKEDIT should drop from ~80 MB to ~20-30 MB on mrmeshpy.so
• Spot-check lief.parse(...).sections on a stripped Linux bundled lib (e.g. libopenvdb.so): .symtab/.strtab should be near zero

🤖 Generated with Claude Code

[Grantim]

Abandoning this approach — the wheel-only strip placement was ineffective (modified the staging dir after python -m build had already frozen the wheel) and the lever should live at build/install time so every distribution benefits, not just wheels. Replacing with a two-PR rollout: PR-A adds add_link_options(-Wl,-x) for macOS Release in CompilerOptions.cmake (our libs); PR-B adds vcpkg triplet -Wl,-s (Linux third-party) and CI brew strip (macOS third-party). See investigation in C:/WORK/claude/wheel-size-investigation.md and plan in C:/WORK/claude/strip-plan.md.