Disable kernel opt by default on Solaris 10 and 11

Disable kernel opt by default on Solaris 10 and 11

With newer Solaris Studio (sometime in the 12.* series), cc started
adding SSE instructions to optimized x86 code, which is invalid for
kernel code and can generate panics. There appears to be no way to
turn this off currently (-xvector=%none is non-functional), so default
to not optimizing kernel code.

Change-Id: I5fdedb11219df68e0146b8e0cee9010c2eb4067e
Reviewed-on: http://gerrit.openafs.org/6671
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementix.org>