We can safely assume that qemu supports -nodefaults and
-no-user-config, since these have been supported since forever.
-no-hpet was deprecated in qemu 8.0 and the option removed in early
2024, replaced with -machine hpet=off. HPET defaults to 'on' in
upstream qemu, and to 'off' in downstream RHEL rebuilds.
Since (for libguestfs) we can assume an up to date Linux kernel is
running inside the guest, and that the kernel will do the right thing
with regards to timers, we don't need to mess with qemu defaults. In
practice, Linux chooses kvm-clock.
Thanks: Thomas Huth, Daniel Berrange
fc243a36bd