Merge branch 'selftests-bpf-improve-libc-portability-musl-support-part-1'

Tony Ambardar says:

====================
selftests/bpf: Improve libc portability / musl support (part 1)

Hello all,

This series includes the bulk of libc-related compile fixes accumulated to
support systems using musl, with smaller numbers to follow. These patches
are simple and straightforward, and the series has been tested with the
kernel-patches/bpf CI and locally using mips64el-gcc/musl-libc and QEMU
with an OpenWrt rootfs.

The patches address a few general categories of libc portability issues:

 - missing, redundant or incorrect include headers
 - disabled GNU header extensions (i.e. missing #define _GNU_SOURCE)
 - issues with types and casting

Feedback and suggestions for improvement are welcome!

Thanks,
Tony
====================

Link: https://lore.kernel.org/r/cover.1721713597.git.tony.ambardar@gmail.com
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>