gradlew does not work with JDK11 or 14

[DFrenkel]

Environment details

• OS: Mac OS (same results on Linux with latest OpenJDK or with OpenJDK 11)
• Java version:

openjdk version "14.0.1" 2020-04-14
OpenJDK Runtime Environment AdoptOpenJDK (build 14.0.1+7)
OpenJDK 64-Bit Server VM AdoptOpenJDK (build 14.0.1+7, mixed mode, sharing)

or

openjdk version "11.0.7" 2020-04-14
OpenJDK Runtime Environment (build 11.0.7+10)
OpenJDK 64-Bit Server VM (build 11.0.7+10, mixed mode)

Steps to reproduce

1. git clone https://github.com/googleapis/discovery-artifact-manager.git
2. cd discovery-artifact-manager/toolkit
3. ./gradlew test

Expected

All tests pass

Actual

FAILURE: Build failed with an exception.

* What went wrong:
Could not determine java version from '14.0.1'.

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

Workaround

Switching to older JDK8

[dazuma]

@DFrenkel This repo is not really being maintained regularly, and most functionality has been migrated elsewhere. What are you trying to do here?

[DFrenkel]

I am trying to test auto-generation some of the code snippets for Google APIs as shown in this PR but on a newer JDK.