Building kernel with clang

[Justin Hibbits]

I'm trying to build kernel with clang on/for ppc64, but running into a
snag.  Doing simply:

make build kernel CC=clang WERROR=

I get the following error when compiling:

/tmp/cam_compat-8U08WY.s: Assembler messages:
/tmp/cam_compat-8U08WY.s:590: Error: unknown pseudo-op: `.cfi_sections'

Anyone know how to fix this?  Do I need to somehow tell it to use the
toolchain in /usr/local?

- Justin