iproute2 and libbpf: vendoring on the small scale

Agreed (though I've no first-hand experience with QEMU itself). What I've done for embedding is default to the internal version, but the flag to use the external version means that it required to be externally provided. This wishy-washy "what is it doing?" kind of questions about build systems are not fun to answer months down the line when you need to debug it.