Remove buildspam from apexer

Turning --verbose off.

Bug: 119768180
Test: m apex.test
[ 99% 5758/5761] //system/apex:apex.test apex [common]
[100% 5761/5761] Install: out/target/product/walleye/system/apex/apex.test.apex

Change-Id: Iddebbbc6a6ad1bc8145abc7878bc310eac4d2792