Do not generate parts of multifile facade when building light classes

Building facade class is enough for this purpose

compiler/backend/src/org/jetbrains/kotlin/codegen/MultifileClassPartCodegen.kt

@@ -43,6 +43,13 @@ public class MultifileClassPartCodegen(
         partContext: FieldOwnerContext<*>,
         state: GenerationState
 ) : MemberCodegen<JetFile>(state, null, partContext, file, v) {
+
+    override fun generate() {
+        if (state.classBuilderMode == ClassBuilderMode.LIGHT_CLASSES) return
+
+        super.generate()
+    }
+
     override fun generateDeclaration() {
         v.defineClass(element, Opcodes.V1_6,
                       Opcodes.ACC_FINAL or Opcodes.ACC_SYNTHETIC,