Add install target to libbpf-tools
Add install target to libbpf-tools

We plan to put those tools in separate rpm,
so we need a way to install them.

Adding install target with standard DESTDIR
and prefix make variables.

Signed-off-by: Jiri Olsa <2c6594f608aa3d41e98d48846a6328831f7084ad@kernel.org>

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