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

compiler/testData/codegen/light-analysis/callableReference/function/genericMember.txt

@@ -1,3 +1,4 @@
+@kotlin.Metadata
 public final class A {
     private final field t: java.lang.Object
     public method <init>(p0: java.lang.Object): void
@@ -5,6 +6,7 @@ public final class A {
     public final method getT(): java.lang.Object
 }
 
+@kotlin.Metadata
 public final class GenericMemberKt {
     public final static @org.jetbrains.annotations.NotNull method box(): java.lang.String
 }