Generate annotations for single-file classes.

compiler/testData/codegen/boxWithStdlib/annotations/fileClassWithFileAnnotation.kt

@@ -0,0 +1,9 @@
+@file:StringHolder("OK")
+@file:JvmName("FileClass")
+
+@Target(AnnotationTarget.FILE)
+@Retention(AnnotationRetention.RUNTIME)
+public annotation class StringHolder(val value: String)
+
+fun box(): String =
+        Class.forName("FileClass").getAnnotation(StringHolder::class.java)?.value ?: "null"