Add constant AT_MINSIGSTKSZ (Cherry-pick libc-0.2 into main)

[ur4t]

rust-lang/rust@9da004e uses AT_MINSIGSTKSZ which is not present in libc crate. AT_MINSIGSTKSZ was introduced since glibc 2.35 on all architectures.

Cherry-pick #3637 into main branch.

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