Fix Bugzilla 24725 - core.sys.linux: feature detect glibc functions a…

[the-horo]

…t build time.

This is just a sample implementation aimed to gather feedback before deciding on the final solution

[dlang-bot]

Thanks for your pull request and interest in making D better, @the-horo! We are looking forward to reviewing it, and you should be hearing from a maintainer soon.
Please verify that your PR follows this checklist:

• My PR is fully covered with tests (you can see the coverage diff by visiting the details link of the codecov check)
• My PR is as minimal as possible (smaller, focused PRs are easier to review than big ones)
• I have provided a detailed rationale explaining my changes
• New or modified functions have Ddoc comments (with Params: and Returns:)

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Bugzilla references

Auto-close	Bugzilla	Severity	Description
✓	24725	enhancement	core.sys.linux: feature detect glibc functions at build time

Testing this PR locally

If you don't have a local development environment setup, you can use Digger to test this PR:

dub run digger -- build "master + dmd#16816"