libmix: Add libMIX environment variables to BoardConfig.mk

BZ: 107291

Move environment variables from libmix makefile to BoardConfig.mk

Change-Id: I430948fe5fd7ae212bb8473c74988a0026a518da
Signed-off-by: Cheng Yao <yao.cheng@intel.com>
Reviewed-on: http://android.intel.com:8080/107838
Reviewed-by: Shi, PingX <pingx.shi@intel.com>
Tested-by: Shi, PingX <pingx.shi@intel.com>
Reviewed-by: cactus <cactus@intel.com>
Reviewed-by: buildbot <buildbot@intel.com>
Tested-by: buildbot <buildbot@intel.com>
8 files changed