add archive reader

[katsyoshi]

Summary

• Add an ar archive reader that parses archive headers and embedded ELF members.
• Support GNU archive symbol tables and long filename tables.
• Parse embedded ELF members lazily through StringIO.
• Add archive inputs to the self linker and extract members that satisfy undefined global symbols.
• Repeat archive extraction until no additional members are required, including transitive member dependencies.
• Add archive fixture helpers and end-to-end coverage using compiled and assembled object files.

Testing

CI is currently broken, so this change was verified with the full test suite locally:

• bundle exec rake test
  • 61 tests, 273 assertions, 0 failures, 0 errors, 1 omission
  • The omitted test requires Ruby::Box, which is not supported in the local environment.

[chatgpt-codex-connector]

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Reviewed commit: 0d9ae2d540

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[katsyoshi]

@codex review

[chatgpt-codex-connector]

💡 Codex Review

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Reviewed commit: d9e7a1696f

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[katsyoshi]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Keep it up!

Reviewed commit: 185a9317ec

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
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• Comment "@codex review".

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