android: export intermediates from libmesa_util

android: export intermediates from libmesa_util

Fixes following build issues:

   In file included from vendor/intel/external/android_ia/mesa/src/mesa/drivers/dri/common/dri_util.c:45:
   vendor/intel/external/android_ia/mesa/src/util/xmlpool.h:103:10: fatal error: 'xmlpool/options.h' file not found
   ...
   In file included from vendor/intel/external/android_ia/mesa/src/mesa/drivers/dri/i965/intel_screen.c:44:
   vendor/intel/external/android_ia/mesa/src/util/xmlpool.h:103:10: fatal error: 'xmlpool/options.h' file not found

Fixes: 601093f9 (xmlconfig: move into src/util)
Signed-off-by: Tapani Pälli <tapani.palli@intel.com>
Reviewed-by: Chih-Wei Huang <cwhuang@linux.org.tw>