Fix make -n use

Due to the way $(MAKE) behaves (it forces execution of the commands
that contain it), use of $(MAKE) in a command line together with
side-effects commands will break stuff. It's better to keep it either
on a separate line, or if not possible, move said commands to a
separate make target.

After this patch, make -n distcheck, make -n regen-vcs-version and
possibly other commands now work correctly.

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Guido Trotter <ultrotter@google.com>