Upgrade gradle-wrapper to > 5.0 to support JDK 11

[PL4typus]

Gradle added support for JDK11 in 5.0.

Currently, using ./gradlew with default-jdk (openjdk-11-jdk) on Debian GNU/Linux bullseye/sid gives the following error:

Unzipping /root/.gradle/wrapper/dists/gradle-3.5-bin/daoimhu7k5rlo48ntmxw2ok3e/gradle-3.5-bin.zip to /root/.gradle/wrapper/dists/gradle-3.5-bin/daoimhu7k5rlo48ntmxw2ok3e
Set executable permissions for: /root/.gradle/wrapper/dists/gradle-3.5-bin/daoimhu7k5rlo48ntmxw2ok3e/gradle-3.5/bin/gradle

FAILURE: Build failed with an exception.

* What went wrong:
Could not determine java version from '11.0.9.1'.

* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output.

[belgattitude]

Can you help with a PR ? Would be fantastic .

[PL4typus]

Can you help with a PR ? Would be fantastic .

I created one just now. I tried updating to the latest version of gradle for gradle-wrapper, but it causes a lot of conflict that I'm afraid I can't solve that easily, as I'm unfamiliar with gradle.

This PR updates to 5.0, which caused less conflicts and still allows to use JDK 11 now.