[PATCH 07/59] posix: Suppress -Wignored-attributes when building for confstr.c with clang

[Florian Weimer]

* Adhemerval Zanella:

> confstr.c:293:1: error: alias will always resolve to __GI___confstr even if weak definition of __GI_confstr is overridden [-Werror,-Wignored-attributes]
>   293 | libc_hidden_def (confstr)
>       | ^

We could introduce static_weak_alias to avoid generating weak
definitions for shared builds.  I think it might even catch some
multiple-definition bugs.

Thanks,
Florian