[K2/N] Read KDoc strings from LightTree nodes

^KT-56090

Merge-request: KT-MR-9613
Merged-by: Vladimir Sukharev <Vladimir.Sukharev@jetbrains.com>

kotlin-native/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/FirNativeSerializer.kt

@@ -68,7 +68,7 @@ internal fun PhaseContext.firSerializer(
                 FirKLibSerializerExtension(
                         session, metadataVersion,
                         ConstValueProviderImpl(input.components),
-                        allowErrorTypes = false, exportKDoc = false
+                        allowErrorTypes = false, exportKDoc = shouldExportKDoc()
                 ),
                 configuration.languageVersionSettings,
         )