Litho gradle build fails with JDK 11

WA is just to drop back to JDK8.

```
$ ./gradlew :sample:installDebug

> Configure project :litho-it
11.0.4 (Oracle Corporation 11.0.4+10-LTS)
null

FAILURE: Build failed with an exception.

* Where:
Build file './litho/litho-it/build.gradle' line: 98

* What went wrong:
A problem occurred evaluating project ':litho-it'.
> java.lang.NullPointerException (no error message)

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

* Get more help at https://help.gradle.org

BUILD FAILED in 1s
```

Fails because Jvm.current().getToolsJar() is null.