tc-testing: use a plugin to build eBPF program

use a TDC plugin, instead of building eBPF programs in the 'setup' stage.
'-B' argument can be used to build eBPF programs in $EBPFDIR directory,
in the 'pre-suite' stage. Binaries are then cleaned in 'post-suite' stage.

Signed-off-by: Davide Caratti <dcaratti@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>