adevice_helper binary for adevice to get device info

New binary that can run on the device that adevice can call to
fingerprint device partitions.

I tried adding a trivial device test, but I ran into into issues as
apparently the test isn't run as root, but some /system dirs are owned
as root.  I need to get the error handling fixed soon, but we need to
add more data to the design doc specifying what should happen.

Test: atest
Test: m adevice_helper && adb push $ANDROID_PRODUCT_OUT/system/bin/adevice_fingerprint /data/bin/adevice_fingerprint &&   adb shell /data/bin/adevice_fingerprint -p system | jq

Change-Id: I30edf433c604f15a13a8abe2476d2018601321d3
4 files changed