For building Invensense HAL for Android L Arm 64bit
$ cd $android_L_root
$ . build/envsetup.sh
$ lunch aosp_flounder-userdebug (or any arm64 target)
$ -> copy Invensense HAL libsensor folder to $android_L_root/hardware/invensense/65xx/
$ -> modifiy the makefile $android_L_root/hardware/invensense/Android.mk to include htc/nvidia flounder target
$ make libinvensense_hal
$ make sensors.flounder
$ adb push $OUT/system/lib/libmllite.so /system/lib/
$ adb push $OUT/system/lib/libinvensense_hal.so /system/lib/
$ adb push $OUT/system/lib/hw/sensors.flounder.so /system/lib/hw/