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

compiler/testData/codegen/light-analysis/extensionFunctions/kt1290.txt

@@ -1,3 +1,4 @@
+@kotlin.Metadata
 public final class Foo {
     private final @org.jetbrains.annotations.NotNull field filter: kotlin.jvm.functions.Function1
     public method <init>(@org.jetbrains.annotations.NotNull p0: kotlin.jvm.functions.Function1): void
@@ -5,6 +6,7 @@ public final class Foo {
     public final @org.jetbrains.annotations.NotNull method getFilter(): kotlin.jvm.functions.Function1
 }
 
+@kotlin.Metadata
 public final class Kt1290Kt {
     public final static @org.jetbrains.annotations.NotNull method box(): java.lang.String
     public final static method foo(): boolean