Kapt3: Write stub class files with metadata (needed for incremental compilation)

compiler/testData/codegen/light-analysis/traits/abstractClassInheritsFromInterface.txt

@@ -1,17 +1,21 @@
+@kotlin.Metadata
 public abstract class KC {
     public method <init>(): void
     public @org.jetbrains.annotations.NotNull method foo(): java.lang.String
 }
 
+@kotlin.Metadata
 public final class KCKt {
     public final static method box(): java.lang.String
 }
 
+@kotlin.Metadata
 public interface T {
     inner class T/DefaultImpls
     public abstract @org.jetbrains.annotations.NotNull method foo(): java.lang.String
 }
 
+@kotlin.Metadata
 public final class T/DefaultImpls {
     inner class T/DefaultImpls
     public static @org.jetbrains.annotations.NotNull method foo(p0: T): java.lang.String