Merge branch 'Use lightweigt version of bpftool'

Pu Lehui says:

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Currently, samples/bpf, tools/runqslower and bpf/iterators use bpftool
for vmlinux.h, skeleton, and static linking only. We can use lightweight
bootstrap version of bpftool to handle these, and it will be faster.

v2:
- make libbpf and bootstrap bpftool independent. and make it simple.

v1: https://lore.kernel.org/bpf/20220712030813.865410-1-pulehui@huawei.com
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Signed-off-by: Andrii Nakryiko <andrii@kernel.org>