Fix Gradle on CI
We were not pinning the version of the Gradle docker image that we were using and had config incompatible with the latest version of Gradle.
I have:
- pinned to version 5.1.0 using the 'slim' image
- fixed the incompatibilities
We were not pinning the version of the Gradle docker image that we were using and had config incompatible with the latest version of Gradle.
I have: