DF-4329 harness build on guest (i915_rcu_harness.ko)
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$ cd /root/kmod/i915rcu && make SYSDIR=/usr/src/sys
i915rcu=0  (cc ... -Werror ... -c i915_rcu_harness.c; link ok)
-rw-r--r-- 1 root wheel 9576 Sep 19 12:19 /root/kmod/i915rcu/i915_rcu_harness.ko
$ kldload /root/kmod/i915rcu/i915_rcu_harness.ko
LOADED=0
i915rcu: loaded (sysctl kern.i915rcu.run=N)