scripts/ksize: Add kernel build size report

ksize generates hierarchical build size reports from vmlinux, *.o, and
built-in.o files.

ksize is useful in preparing minimal configurations and comparing
similar configurations across kernel versions.

Signed-off-by: Darren Hart <dvhart@linux.intel.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Josh Triplett <josh@joshtriplett.org>