Provide simple environment variables telling which stage of boot is
being built. Also move this to arch-agnostic location.
Change-Id: I8cbb5cf91f53e01c06e7d672b5be3f5c235f911d
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: http://review.coreboot.org/5410
Reviewed-by: Aaron Durbin <adurbin@google.com>
Tested-by: build bot (Jenkins)