`res_search` became a proper symbol only in glibc 2.34. Until that it
was re-defined in headers, hitting the (in-)famous
https://github.com/ziglang/zig/issues/9485
glibc 2.34+:
resolv/resolv.h:int res_search (const char *, int, int, unsigned char *, int)
Old glibc:
resolv/resolv.h:#define res_search __res_search
Also, remove the toplevel includes, as they should never be included in
the first place: the headers are included explicitly when needed.
`zig cc` emits `--gc-sections` for the linker, which is incompatbile
with what CGo thinks about linking.
This commit adds a workaround: it will add `--no-gc-sections` to the
linking step if the command is not specified (falling back to the
default behavior of gcc/clang).
Related: https://github.com/golang/go/issues/52690
