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

compiler/testData/codegen/light-analysis/dataClasses/copy/withGenericParameter.txt

@@ -1,3 +1,4 @@
+@kotlin.Metadata
 public final class A {
     private final @org.jetbrains.annotations.NotNull field a: Foo
     public method <init>(@org.jetbrains.annotations.NotNull p0: Foo): void
@@ -10,12 +11,14 @@ public final class A {
     public method toString(): java.lang.String
 }
 
+@kotlin.Metadata
 public final class Foo {
     private final field a: java.lang.Object
     public method <init>(p0: java.lang.Object): void
     public final method getA(): java.lang.Object
 }
 
+@kotlin.Metadata
 public final class WithGenericParameterKt {
     public final static @org.jetbrains.annotations.NotNull method box(): java.lang.String
 }