Build bcc with libbpf package
    
    Now when we have libbpf packaged we want it to be used to build bcc,
    instead of libbpf Github repo, which is downloaded during the build.
    
    The bcc still produces libbcc.so/libbcc.a with libbpf code inside,
    so nothing changes there.. apart from that they are built from libbpf
    package now instead of libbpf Github repo
    
    The addition is libbcc-no-libbpf.so library, which will be used in
    applications like bpftrace which needs to link libbpf.so by itself
    for other features.
    
    Signed-off-by: Jiri Olsa <jolsa@redhat.com>