libbpf tools: check in bpftool for use by libbpf-based tool build
libbpf tools: check in bpftool for use by libbpf-based tool build

Check in bpftool binary to be used for BPF skeleton generation for
libbpf-based tools.

Signed-off-by: Andrii Nakryiko <1ab6096f60c2d8d3f6ff85bf25d0ee81fb25b434@fb.com>

iovisor/bcc,iovisor/bcc,tuxology/bcc,tuxology/bcc,iovisor/bcc,brendangregg/bcc,brendangregg/bcc,brendangregg/bcc,brendangregg/bcc,iovisor/bcc,iovisor/bcc,brendangregg/bcc,tuxology/bcc,tuxology/bcc,tuxology/bcc