update build.sh to use the latest toolchain

Change-Id: I2b9e021e90a356fd35bae87abe5d0c37f28458ae
config: enable memory group

Required for optimal functionality of ZRAM
http://source.android.com/devices/low-ram.html

Change-Id: Ic77c0766b32dc4588124a8d97e208c96d6125622