fix(geomodel): hide std::__format exports via linker version script

[olantwin]

Summary

• Adds a linker version script that marks every _ZNSt8__format* symbol as local in geomodel's shared libraries, passed via CMAKE_SHARED_LINKER_FLAGS.
• Bumps recipes/geomodel/recipe.yaml build.number to 3.

Why

Round 1 (#15) rebuilt geomodel against the current conda-forge cxx-compiler (no source change, only build.number). Round 2 (#16) added -fvisibility-inlines-hidden. Neither removed the four weak std::__format::_Sink_iter<char> template instantiations that libGeoModelXml, libGeoModelWrite, libGeoModelRead, and libGeoModelDBManager keep exporting:

_ZNSt8__format14__write_padded…
_ZNSt8__format15__write_escaped…
_ZNSt8__format22__write_padded_as_spec…
_ZNSt8__format23__write_escaped_unicode…

libstdc++.so.6 does not export strong overrides, so these weak duplicates remain the only definitions visible to the dynamic linker — and subtle libstdcxx-devel header drift between the geomodel build host and downstream consumers crashes build_geometry inside Gmx2Geo on GitHub Actions (ShipSoft/Geometry#26) while passing on developer machines. -fvisibility-inlines-hidden doesn't affect these because they're standalone template instantiations, not class member inlines; objcopy --localize-symbol/--strip-symbol on the built .sos leaves the .dynsym entries untouched (verified with readelf -W --dyn-syms before/after).

A linker version script applied at link time is the standard way to control DSO exports. Confirmed locally with a minimal extern "C" std::string fmt_it(int i) { return std::format("v={}", i); } test: 81 weak _ZNSt8__format exports drops to 0 with -Wl,--version-script={ local: _ZNSt8__format*; };. Each consumer (libGeoModelXml's own internal calls, build_geometry's own calls) keeps its translation-unit-local instantiation compiled against its own contemporaneous libstdc++ headers — no cross-library ABI dependency.

Test plan

• CI build job succeeds for the geomodel/shipgeometry/shipgeometryservice/aegir tier
• After merge, post-merge run uploads geomodel 6.27.0 hb0f4dca_3 to channel ship
• nm -D reports 0 weak _ZNSt8__format exports in each of libGeoModelXml/Write/Read/DBManager.so.6
• pixi run test in Geometry/ passes locally, and PR build: rebuild geant4-dependent recipes against geant4 11.4 #26's GitHub Actions run goes green on ubuntu-latest

Summary by CodeRabbit

• Chores
  • Updated build configuration to optimize library symbol handling and incremented package version.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: e1c54716-ccfd-43bc-bd8a-b6fb77e538c6

📥 Commits

Reviewing files that changed from the base of the PR and between 5062c4e and 508e2fb.

📒 Files selected for processing (2)

• recipes/geomodel/build.sh
• recipes/geomodel/recipe.yaml

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📝 Walkthrough

Walkthrough

This PR modifies the geomodel conda recipe build configuration to enforce C++ symbol visibility. The build script now generates a linker version script that marks std::__format* symbols as local, passed to CMake to prevent weak template duplicates from being exposed in shared libraries. The recipe build number is incremented to reflect this rebuild.

Changes

Symbol Visibility Enforcement

Layer / File(s)	Summary
Linker version script generation and CMake integration recipes/geomodel/build.sh	Build script generates hide-std-format.ver to localize std::__format* symbols and integrates it into CMake via CMAKE_SHARED_LINKER_FLAGS, ensuring weak format template instantiations are hidden at link/load time.
Build number increment recipes/geomodel/recipe.yaml	Recipe metadata build number incremented from 2 to 3 to reflect the rebuild with updated linker configuration.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The pull request title accurately describes the main change: hiding std::__format symbols via a linker version script in the geomodel build process.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/geomodel-version-script

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