review: update compareBuilds script

[David Hill]

Kevin,
an update to a utility script that compares build outputs

jbs: https://bugs.openjdk.java.net/browse/JDK-8171326

webrev: http://cr.openjdk.java.net/~ddhill/8171326.1 <http://cr.openjdk.java.net/%7Eddhill/8171326.1>

-- 
David Hill<David.Hill at Oracle.com>
Java Embedded Development

"A man's feet should be planted in his country, but his eyes should survey the world."
-- George Santayana (1863 - 1952)