Make JVM target explicit in sentry-core

[dilbernd]

IDEA’s gradle support failed to inherit language/bytecode level from
parent project, causing mockito failures w/ 11 bytecode.

📢 Type of change

• Bugfix
• New feature
• Enhancement
• Refactoring

📜 Description

Explicitly set Java / JVM versions for the sentry-core subproject.

💡 Motivation and Context

Technically it doesn’t fix a Sentry bug but rather papers over a bug in IDEA 2020.1.2 which makes tests fail from the IDE: It doesn’t detect the source & target JVM versions from the parent project. Then it generates JVM 11 bytecode, which our Mockito can’t handle.

💚 How did you test it?

Reimported in IDEA 2020.1.2 and saw that the JVM versions were now correct in the settings & the tests were green.

Had some tests that did not seem to deliver any result (green or red) in AS 4.0 but this did not change after reverting this change locally so it’s at least unrelated.

📝 Checklist

• I reviewed submitted code
• I added tests to verify changes - ⚠️ Build config only
• All tests passing

🔮 Next steps

[bruno-garcia]

LGTM but this is really up to @marandaneto

[dilbernd]

Forgot to note under “how tested”: Local ./gradlew clean test on OpenJDK Runtime Environment (Zulu 8.46.0.19-CA-macosx) (build 1.8.0_252-b14) also ran through.

[marandaneto]

ideally, we'd set this on allprojects but I remember having issues with Kotlin DSL, it works just fine using Groovy though, let's bring this in and I'll check if they already fixed the compatibility with Groovy Clojures and Kotlin DSL.
thanks for the fix @dilbernd