user should be warned that qemu 2.9 is min. version that we want to support

[eyberg]

ops currently bails out if cpu max is not present - this was observed on centos 7.5.1804

being that qemu is on version 6.0 and we've already done upstream patches we should ask user to upgrade - if on mac we could flash the brew tap upgrade line that we've prepared

https://github.com/nanovms/ops/issues/505

https://github.com/nanovms/nanos/wiki/qemu