Merge branch 'strip-mods-from-global-vars'

Andrii Nakryiko says:

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Fix bpftool logic of stripping away const/volatile modifiers for all global
variables during BPF skeleton generation. See patch #1 for details on when
existing logic breaks and why it's important. Support special .strip_mods=true
mode in btf_dump__emit_type_decl.

Recent example of when this has caused problems can be found in [0].

  [0] https://github.com/iovisor/bcc/pull/2994#issuecomment-650588533
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Signed-off-by: Alexei Starovoitov <ast@kernel.org>