[Integrated] RFR: Add testReport task to create a combined report

[Robin Westberg]

Changeset: ef749307
Author:    Robin Westberg <rwestberg at openjdk.org>
Date:      2020-04-08 11:24:11 +0000
URL:       https://git.openjdk.java.net/skara/commit/ef749307

Add testReport task to create a combined report

Reviewed-by: ehelin

! build.gradle