[Integrated] RFR: Make build incremental

[duke]

Changeset: 65f57288
Author:    Erik Helin <ehelin at openjdk.org>
Date:      2019-09-24 14:08:32 +0000
URL:       https://git.openjdk.java.net/skara/commit/65f57288

Make build incremental

Reviewed-by: rwestberg

! build.gradle
! buildSrc/images/src/main/java/org/openjdk/skara/gradle/images/DownloadJDKTask.java
! buildSrc/images/src/main/java/org/openjdk/skara/gradle/images/ImagesPlugin.java
! buildSrc/images/src/main/java/org/openjdk/skara/gradle/images/LaunchersTask.java
! buildSrc/images/src/main/java/org/openjdk/skara/gradle/images/LinkTask.java
! buildSrc/module/src/main/java/org/openjdk/skara/gradle/module/ModulePlugin.java