This commit fixes KT-33028 by not setting empty boot classpath when
running on JDK9+. When compiling with -source 8 and below, this allows
classes from java.base module to be available in the boot classpath.
This commit also fixes KT-33050 by passing the source level of Java compile
task in the KAPT javac options. This is important as some annotation processors
are using ProcessingEnvironment.getSourceVersion() in order to decide what
code to generate.
Test: Kapt3IT test added for worker and non-worker invocations
Ivan Gavrilovic
f3acd8d10c