Mixed-Mode compilation - Compile Java and Kotlin in one pass in the worker.

[hsyed]

The rules should be able to compile Java and Kotlin files in a single pass. Support has already been added, it needs to be further tested and refined. A lot of the work done for this is needed for annotation processing / kapt support.

Notes on implementation:

• Java compilation only occurs when there is a Java source file present.

RFC:

* Workers creates a temp directory and compiles to that -- Is this ok to do ?

Todo:

• Java compiler used by Kotlins prints out a pointless 1 java file compiled to to the console -- need to silence this without silencing anything else.
• Verify warning and error reporting, the warnings and errors need to get to intellij / the console.
• [ ] Mirror the compilation switches and classpath setup that is in use by the Java rules -- As far as Java compilation goes we should have same experience -- Whatever Linting is configured for Java core, it should work when Kotlin is compiling Java -- Could use help on this one as it will remain a bit low on my list of priorities. unrealistic

[hsyed]

The correct approach to mixed mode is to compile in 2 phases. Unless something has changed in recent releases. Kotlinc only compiles java sources that it has analysed. I think it makes sense to just leave all java compilation to javac.