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>

configure.ac

@@ -18,6 +18,11 @@ AC_CONFIG_AUX_DIR([bin])
 AC_CANONICAL_HOST
 AM_INIT_AUTOMAKE([foreign])
 
+# Support silent build rules, requires at least automake-1.11. Disable
+# by either passing --disable-silent-rules to configure or passing V=1
+# to make
+m4_ifdef([AM_SILENT_RULES], [AM_SILENT_RULES([yes])])
+
 LT_PREREQ([2.2])
 LT_INIT([disable-static])