makefile and run_tests tweaks

- remove a redundant '-display none'
- remove a redundant -g from CFLAGS
- remove a useless -I../include/x86 from CFLAGS
- remove lib autodep files on make clean

Signed-off-by: Andrew Jones <drjones@redhat.com>
Acked-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>