[llvm-branch-commits] [NFC][sanitizer] Switch to `gnu_get_libc_version` (PR #108724)

[Vitaly Buka via llvm-branch-commits]

https://github.com/vitalybuka created https://github.com/llvm/llvm-project/pull/108724

`gnu_get_libc_version` unlike `confstr` is not
intercepted. We should be able to use this
function earier.

Looks like we use `confstr` staring from
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60038
but there is no specific reason to refer it over
`gnu_get_libc_version`.