glibc: add backwards compatibility for some symbols

[motiejus]

• fcntl was renamed to fcntl64 in glibc 2.28 (see glibc 2.27 or older: fcntl64 not found, but zig's glibc headers refer it #9485)
• res_{,n}{search,query,querydomain} became "their own" symbols since glibc 2.34: they were prefixed with __ before.

This PR makes it possible to use fcntl with glibc 2.27 or older and the res_* functions with glibc 2.33 or older.

These patches will become redundant with universal-headers and can be dropped. But we have to do with what we have now.

Closes #9485

Related: 39083c3

[marler8997]

Besides the test you added, is there anything else we can do to make the upgrade path easier here. Sounds like a pain to upgrade glibc, then have to debug this failing test and try to slueth out that you need to re-apply this diff.

[motiejus]

Besides the test you added, is there anything else we can do to make the upgrade path easier here. Sounds like a pain to upgrade glibc, then have to debug this failing test and try to slueth out that you need to re-apply this diff.

Good question. I will make this a bit easier to apply:

• separate the commit to glibc and the test
• collect all such commits to a single place, like lib/libc/glibc/ZIG-PATCHES.md. AFAIK we have one right now, this will be the second one.

[BratishkaErik]

btw this might be useful https://wiki.gentoo.org/wiki/Project:Toolchain/Porting_notes#glibc

[andrewrk]

Besides the test you added, is there anything else we can do to make the upgrade path easier here. Sounds like a pain to upgrade glibc, then have to debug this failing test and try to slueth out that you need to re-apply this diff.

Hello, it's me from the future. It's no problem at all since the documented process tells you to run git log -- lib/libc/glibc lib/libc/include and inspect the commits since the last update, looking for patches to re-apply.