mesa: Enable silent automake rules when available.

mesa: Enable silent automake rules when available.

Finally, a quiet build for the i965 driver, at least!  (Note, you can
still get verbose builds at build-time by saying "make V=1")

Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>
Reviewed-by: Chad Versace <chad.versace@linux.intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>