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

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

@@ -1,9 +1,11 @@
+@kotlin.Metadata
 public final class A {
     public method <init>(): void
     public final method k(p0: int): int
     public final method o(): int
 }
 
+@kotlin.Metadata
 public final class ClassMemberFromExtensionKt {
     public final static @org.jetbrains.annotations.NotNull method box(): java.lang.String
     public final static method foo(@org.jetbrains.annotations.NotNull p0: A): int