Saving build durations as numbers instead of formatted timestamps
Saving build durations as numbers instead of formatted timestamps

Now, a build metrics file might look like this:

  {"configuration_duration": 0.774, "task_execution_duration": 86.44, "total_cpu": 1072.12}

Bug: 148526619
Test: DIST_DIR=../../out/dist ./busytown/androidx.sh
Change-Id: Ia13004c6f933db9018ef111d355e95e9ef17ac89

AndroidX/androidx,androidx/androidx,AndroidX/androidx,AndroidX/androidx,AndroidX/androidx,androidx/androidx,AndroidX/androidx,androidx/androidx,AndroidX/androidx,androidx/androidx,AndroidX/androidx,AndroidX/androidx,androidx/androidx,androidx/androidx,AndroidX/androidx,androidx/androidx,androidx/androidx,androidx/androidx,AndroidX/androidx,androidx/androidx