Address (java) build warnings

[tellypresence]

When building project integrating Cardboard SDK, get build warnings e.g.

> Task :cardboardsdk:compileDebugJavaWithJavac
warning: [options] source value 8 is obsolete and will be removed in a future release
warning: [options] target value 8 is obsolete and will be removed in a future release
warning: [options] To suppress warnings about obsolete options, use -Xlint:-options.
3 warnings

Would be nice to make those go away if possible

[rjcausarano]

Thank you @tellypresence for reporting this issue. I confirm I’m able to reproduce the issue locally. It has been added to our backlog and will be prioritized along with other issues. We'll update this issue once we have some updates about it.

[Voldivh]

These warnings were being generated by the gradle version we were using. They should be fixed on the upcoming release 1.31.0. Thanks for the patience and for reporting this!

[xinyunh0929]

This was fixed in v1.31.0.