[Integrated] RFR: Update to Gradle 6.0

[Erik Helin]

Changeset: 49bbd418
Author:    Erik Helin <ehelin at openjdk.org>
Date:      2019-11-11 13:23:45 +0000
URL:       https://git.openjdk.java.net/skara/commit/49bbd418

Update to Gradle 6.0

Reviewed-by: rwestberg

! buildSrc/build.gradle
! cli/build.gradle
! deps.env