Android Sensor HAL

Trying to get an Invensense MPU-9250 working with Android (CAF Oreo) on a SOM that also has the Snapdragon 820. Found a driver and that looks to be working just fine (cat /sys/bus/iio/iio:device0/regdump gives non-zero values when the device is connected, otherwise all zeros)). Now the next step is getting it connected to the OS through the Android Sensors HAL. I found some code under hardware/invensense/65xx, which is pretty much the same IC without the magnetometer, so that should be fine. However, I can’t find any good documentation on how to get this compiled, included in my image and hooked up to my iio:device0. As far as I understand it should spit out some shared libs under out/target/system and out/target/system/hw, but they are not generated. When I run mmm inside hardware/invensense/65xx/libsensors_iio I get the following error:

ninja: error: 'out/target/product/msm8996/obj_arm/SHARED_LIBRARIES/libmllite_intermediates/export_includes', needed by 'out/target/product/msm8996/obj_arm/SHARED_LIBRARIES/sensors.msm8996_intermediates/import_includes', missing and no known rule to make it  

Is there anybody here that has experience with this? Thanks!