glibc 2.42 support

[alexrp]

https://sourceware.org/glibc/wiki/Release/2.42

Planned release date is 1st of August (i.e. in a week), so we should try to get this into 0.15.0.

[alexrp]

Arrived a bit earlier than expected: https://sourceware.org/pipermail/libc-alpha/2025-July/168994.html