ProGuard complains if we're trying to shrink compiler with the full runtime in
dependencies because for the compiler produced on the first step of bootstrap
these two jars contain conflicting classes. This won't matter in the final
distribution because we will strip 'core' modules from compiler.jar. But this
matters in the first step because core will be different in the compiler (used
to load compiled class files) and in the reflection (used to introspect symbols
at runtime).
kotlin-runtime-minimal.jar still contains the complete reflection API and some
stub implementations in module 'reflection.stub.jvm', but doesn't have core, so
it won't cause a proguard error
Alexander Udalov