(minor) Move source set configuration creation

It was placed in the new MPP plugin and was therefore not used for
the 'KotlinSourceSet's with the old plugin. Move this logic to the
KotlinSourceSetFactory so that it is applied to all source sets

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/plugin/mpp/KotlinMultiplatformPlugin.kt

@@ -103,7 +103,6 @@ internal class KotlinMultiplatformPlugin(
     }
 
     private fun configureSourceSets(project: Project) = with (project.kotlinExtension as KotlinMultiplatformExtension) {
-        sourceSets.all { defineSourceSetConfigurations(project, it) }
         val production = sourceSets.create(KotlinSourceSet.COMMON_MAIN_SOURCE_SET_NAME)
         val test = sourceSets.create(KotlinSourceSet.COMMON_TEST_SOURCE_SET_NAME)
 
@@ -156,10 +155,4 @@ internal class KotlinMultiplatformPlugin(
             }
         }
     }
-
-    private fun defineSourceSetConfigurations(project: Project, sourceSet: KotlinSourceSet) = with (project.configurations) {
-        sourceSet.relatedConfigurationNames.forEach { configurationName ->
-            maybeCreate(configurationName)
-        }
-    }
 }

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/plugin/sources/KotlinSourceSetFactory.kt

@@ -28,8 +28,13 @@ internal abstract class KotlinSourceSetFactory<T : KotlinSourceSet> internal con
         project.file("src/$sourceSetName")
 
     protected open fun setUpSourceSetDefaults(sourceSet: T) {
-        with(sourceSet) {
-            sourceSet.kotlin.srcDir(File(defaultSourceLocation(sourceSet.name), "kotlin"))
+        sourceSet.kotlin.srcDir(File(defaultSourceLocation(sourceSet.name), "kotlin"))
+        defineSourceSetConfigurations(project, sourceSet)
+    }
+
+    private fun defineSourceSetConfigurations(project: Project, sourceSet: KotlinSourceSet) = with (project.configurations) {
+        sourceSet.relatedConfigurationNames.forEach { configurationName ->
+            maybeCreate(configurationName)
         }
     }