Add libbpf to dependencies (#2436)
Add libbpf to dependencies (#2436)

Add instructions to the readme to avoid confusion about libbpf.
mbudiu-vmw/p4c-clone,mbudiu-vmw/p4c-clone,p4lang/p4c,p4lang/p4c,mbudiu-vmw/p4c-clone,p4lang/p4c,mbudiu-vmw/p4c-clone,p4lang/p4c,p4lang/p4c