With [0], pahole can now discover kfuncs and inject DECL_TAG
into BTF. With this commit, we will start shipping said DECL_TAGs
to downstream consumers if pahole supports it.

This is useful for feature probing kfuncs as well as generating
compilable prototypes. This is particularly important as kfuncs
do not have stable ABI.

[0]: https://git.kernel.org/pub/scm/devel/pahole/pahole.git/commit/?id=72e88f29c6f7e14201756e65bd66157427a61aafSigned-off-by: Daniel Xu <dxu@dxuuu.xyz>
Link: https://lore.kernel.org/r/324aac5c627bddb80d9968c30df6382846994cc8.1718207789.git.dxu@dxuuu.xyzSigned-off-by: Alexei Starovoitov <ast@kernel.org>