Suggest add extra args for qemu

[coolgw]

Thanks for your great work, i have tried and it has great help to build env debug kernel!

Normally i need ssh to qemu so i normally configure some extra args for network part such as:
network_args="-device e1000,netdev=net0 -netdev user,id=net0,hostfwd=tcp::5555-:22"

Also direct output to serial with following args.
serial_args="-nographic -serial mon:stdio"

Since i use Virtual box as host and create qemu instance within virtual box so i have to disable -enable-kvm, and add
no-apic vdso=0, just FYI.