Merge branch 'libbpf-support-multi-split-btf'

Alan Maguire says:

====================
libbpf: support multi-split BTF

In discussing handling of inlines in BTF [1], one area which we may need
support for in the future is multiple split BTF, where split BTF sits
atop another split BTF which sits atop base BTF.  This two-patch series
fixes one issue discovered when testing multi-split BTF and extends the
split BTF test to cover multi-split BTF also.

[1] https://lore.kernel.org/dwarves/20250416-btf_inline-v1-0-e4bd2f8adae5@meta.com/
====================

Link: https://patch.msgid.link/20250519165935.261614-1-alan.maguire@oracle.com
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>