Merge branch 'bpf-libbpf-cleanups'

Jesper Dangaard Brouer says:

====================
This patchset contains some small improvements and cleanup for
the Makefile in tools/lib/bpf/.

It worries me that the libbpf.so shared library is not versioned,
but it not addressed in this patchset.
====================

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>