tools: making test compilation efficient
tools: making test compilation efficient

This CL speeds up "veyron-go-test" from 2m30s to 1m on my machine.

Change-Id: Ie35c6b65cfb1caf8b25469c03fd35d2fb061ed4f

vanadium/go.devtools,vanadium/go.devtools,vanadium/go.devtools