Merge branch 'libbpf: Fix BTF dump of pointer-to-array-of-struct'

Jean-Philippe Brucker says:

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Fix an issue with the libbpf BTF dump, see patch 1 for details.

Since [v1] I added the selftest in patch 2, though I couldn't figure out
a way to make it independent from the order in which debug info is
issued by the compiler.

[v1]: https://lore.kernel.org/bpf/20210318122700.396574-1-jean-philippe@linaro.org/


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Signed-off-by: Andrii Nakryiko <andrii@kernel.org>