[Swan-dev] Heads up KVM tweaks

[Andrew Cagney]

FYI,

I made the below tweaks to how KVMs are built.  It also should
automatically update (...), and building should be faster overall.
If you're not already setting KVM_WORKERS in Makefile.inc.local,
there's now another incentive - the heuristic is #cores/2.

Andrew

kvm: use KVM_WORKERS as heuristic for beefing up build machine

    (KVM_WORKERS defaults to 1)

    Memory: change 2048 to
      1024+2*512*$(KVM_WORKERS)
    (a test requires 2*512mb VMs * $(KVM_WORKERS))

    CPU: change 2 to
      $(KVM_WORKERS)
    which means the default is 1 (the heuristic is #cores/2 so
    that assumed a 4-core machine).

    Make: use the #CPUs+1 heuristic vis:
      -j $(KVM_WORKERS)+1