kbuild: try readelf first in gen_symversions

[opsiff]

deepin inclusion
category: performance

Instead of nm, readelf is more faster, and significantly improve build speed when enable CONFIG_GENKSYMS.

Summary by Sourcery

Enhancements:

• Optimize symbol version generation by using readelf before falling back to nm, reducing overhead during builds with CONFIG_GENKSYMS enabled.

[sourcery-ai]

Reviewer's guide (collapsed on small PRs)

Reviewer's Guide

Switches gen_symversions in the kernel build system to prefer readelf over nm for extracting symbol information, aiming to improve build performance when CONFIG_GENKSYMS is enabled.

File-Level Changes

Change	Details	Files
Prefer readelf over nm in gen_symversions to speed up symbol version generation with CONFIG_GENKSYMS.	Update the gen_symversions command pipeline to invoke readelf as the primary tool for reading symbol information. Retain nm as a fallback (if implemented) to preserve compatibility where readelf may not behave as expected. Adjust any related build logic or conditionals in the kbuild scripts to reflect the new tool preference.	scripts/Makefile.build

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[Avenger-285714]

it's suggested to try to send it upstream

[Avenger-285714]

/approve

[deepin-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Avenger-285714

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• deepin/OWNERS [Avenger-285714]

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[Copilot]

Pull request overview

This PR changes the export-symbol probe in gen_symversions from nm to readelf -sW to speed up builds when CONFIG_MODVERSIONS is enabled. The check runs once per compiled object that may export symbols, so using the faster readelf reduces overall build time.

Changes:

• Replace $(NM) $@ with $(READELF) -sW $@ for the __export_symbol_ probe in the gen_symversions helper.
• Drop the leading space from the grep pattern (since readelf -sW formats output differently than nm).

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