Makefile.proof: Reorder theorem provers

Prefer Z3 over CVC4, the latter seems to not do anything for the current
code and just wastes CPU cycles.

Change-Id: Ia5e1341e881c5f887452486a318e8e72513f28fb
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/20627
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Adrian-Ken Rueegsegger <ken@codelabs.ch>
1 file changed