bpftools: update, split off bpftool and libbpf packages

bpftools: update, split off bpftool and libbpf packages

My original bpftools package made "variant" builds of bpftool and libbpf
as a convenience, since both used the same local kernel sources with the
same versioning. This is no longer the case, since the commit below
switched to using an out-of-tree build mirror hosting repos for each.

Replace bpftools with separate bpftool and libbpf packages, each simplified
and correctly versioned. Also fix the broken libbpf ABI introduced in the
same commit. Existing build .config files are not impacted.

Fixes: 00cbf6f6ab1d ("bpftools: update to standalone bpftools + libbpf, use the latest version")
Signed-off-by: Tony Ambardar <itugrok@yahoo.com>
(cherry picked from commit afe1bf11f2539f75e30ab3206891dbe6f8c43bd5)
Signed-off-by: Daniel Golle <daniel@makrotopia.org>