[skara] RFR: build: use included build instead of buildSrc

[Robin Westberg]

On Wed, 10 Feb 2021 10:44:44 GMT, Erik Helin <ehelin at openjdk.org> wrote:

> Hi all,
> 
> please review this small patch that makes the build use "included builds" for Skara's Gradle plugins instead of the "buildSrc" feature of Gradle. The "buildSrc" feature doesn't play nice with Gradle's caching mechanism - any change to a file in the `buildSrc` directory invalidates the build cache. The solution is to just include the plugins using the `includeBuild` feature (the Gradle team is even thinking of making `buildSrc` an implicitly included build, see https://github.com/gradle/gradle/issues/2531).
> 
> Testing:
> - [x] `make images` on Linux x64
> - [x] `make test` on Linux x64
> 
> Thanks,
> Erik

Good stuff!

-------------

Marked as reviewed by rwestberg (Reviewer).

PR: https://git.openjdk.java.net/skara/pull/1004