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

compiler/testData/codegen/light-analysis/enum/enumShort.txt

@@ -1,3 +1,4 @@
+@kotlin.Metadata
 public enum class Color {
     public final static field BLUE: Color
     public final static field GREEN: Color
@@ -9,6 +10,7 @@ public enum class Color {
     public static method values(): Color[]
 }
 
+@kotlin.Metadata
 public final class EnumShortKt {
     public final static @org.jetbrains.annotations.NotNull method box(): java.lang.String
     public final static method foo(): int