Kapt: Register additional source directories without modifying the raw Gradle model

Unfortunately, this works only for the newer Android Studio versions, so we need to keep the old code until IDEA will migrate at least to AS 3.1.

plugins/kapt3/kapt3-idea/src/org/jetbrains/kotlin/kapt/idea/KaptProjectResolverExtension.kt

@@ -110,11 +110,16 @@ class KaptProjectResolverExtension : AbstractProjectResolverExtension() {
         ideModule.findAndroidModuleModel()?.let { androidModelAny ->
             // We can cast to AndroidModuleModel cause we already checked in findAndroidModuleModel() that the class exists
 
+            val generatedKotlinSources = sourceSet.generatedKotlinSourcesDirFile ?: return
+
             val androidModel = androidModelAny.data as? AndroidModuleModel ?: return
             val variant = androidModel.findVariantByName(sourceSet.sourceSetName) ?: return
 
+            androidModel.registerExtraGeneratedSourceFolder(generatedKotlinSources)
+
+            // TODO remove this when IDEA eventually migrate to the newer Android plugin
             try {
-                sourceSet.generatedKotlinSourcesDirFile?.let { variant.mainArtifact.generatedSourceFolders += it }
+                variant.mainArtifact.generatedSourceFolders += generatedKotlinSources
             } catch (e: Throwable) {
                 // There was an error being thrown here, but the code above doesn't work for the newer versions of Android Studio 3
                 // (generatedSourceFolders returns a wrapped unmodifiable list), and the thrown exception breaks the import.