metricsd: Add Android.mk.

This builds:
* metrics_client: command line interface to log metrics.
* libmetrics: shared library used by services to log metrics.
* metrics_daemon: background daemon responsible for aggregating the
  metrics log and upload it periodically.

BUG: 22879597

Change-Id: I79adc4953d5bfd541df955fbc77d3549f5bbd26b
1 file changed