README: add libxml2 and libpciaccess packages to list or required packages
README: add libxml2 and libpciaccess packages to list or required packages

Needed for link stage.

raphaelsc/scylla,scylladb/scylla,duarten/scylla,avikivity/scylla,raphaelsc/scylla,avikivity/scylla,avikivity/scylla,kjniemi/scylla,scylladb/scylla,kjniemi/scylla,kjniemi/scylla,raphaelsc/scylla,scylladb/scylla,duarten/scylla,scylladb/scylla,duarten/scylla