Kernel build fails with invariants disabled.

[Adam Sakareassen <lists_dfly@xxxxxxxxxxxxxxxx>]

The kernel fails to build on my system with the "options INVARIANTS" 
disabled in the configuration.

It fails to build sys/kern/kern_spinlock.c

(System installed from pre-release 3.2 iso image.  Source updated to 
master.)

No issue for me, I was just playing around with config options. I have 
just re-enabled it.