[BEAM-3249] Update the build script to be compatible with building Gradle within Google

[lukecwik]

• Revert the extraMavenUrls since it isn't needed.
• Disable the build scan plugin when running in offline mode.

---

Follow this checklist to help us incorporate your contribution quickly and easily:

• Format the pull request title like [BEAM-XXX] Fixes bug in ApproximateQuantiles, where you replace BEAM-XXX with the appropriate JIRA issue, if applicable. This will automatically link the pull request to the issue.
• If this contribution is large, please file an Apache Individual Contributor License Agreement.

It will help us expedite review of your Pull Request if you tag someone (e.g. @username) to look at it.

Post-Commit Tests Status (on master branch)

Lang	SDK	Apex	Dataflow	Flink	Gearpump	Samza	Spark
Go		---	---	---	---	---	---
Java
Python		---		---	---	---	---

[lukecwik]

R: @markflyhigh
CC: @kennknowles @pabloem

[kennknowles]

Does build scan require online access just to be on the classpath? or just to be applied? My impression was the answer to both is "no". But whatever works. The other changes seem good since $GRADLE_HOME/init.d suffices for sandbox builds.

[lukecwik]

Your correct in saying that you don't need to be online to apply it as it disables itself and also won't run without --scan present. The issue is that we aren't sure what license the code is being distributed under and can't use it inside Google till the licensing question is resolved. The open source portion of Gradle is under Apache 2.0 but the build-scan plugin isn't open source and it is unclear what the license is, asked on the Gradle forum: https://discuss.gradle.org/t/what-is-the-build-scan-plugin-source-code-license/27585

[pabloem]

Thanks Luke. This LGTM.

[markflyhigh]

Thank you! LGTM

[kennknowles]

Nice find. How unfortunate.