[Interop][Serialization] Skip files with C enums and structs

We don't need to serialize these files since stubs for enums and structs
will be generated anew.

backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/ir/interop/IrProviderForCEnumAndCStructStubs.kt

@@ -116,9 +116,13 @@ internal class IrProviderForCEnumAndCStructStubs(
     private fun irParentFor(descriptor: ClassDescriptor): IrDeclarationContainer {
         val packageFragmentDescriptor = descriptor.findPackage()
         return filesMap.getOrPut(packageFragmentDescriptor) {
-            IrFileImpl(NaiveSourceBasedFileEntryImpl("CTypeDefinitions"), packageFragmentDescriptor).also {
+            IrFileImpl(NaiveSourceBasedFileEntryImpl(cTypeDefinitionsFileName), packageFragmentDescriptor).also {
                 this@IrProviderForCEnumAndCStructStubs.module?.files?.add(it)
             }
         }
     }
+
+    companion object {
+        const val cTypeDefinitionsFileName = "CTypeDefinitions"
+    }
 }

backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/serialization/KonanIrModuleSerializer.kt

@@ -3,6 +3,7 @@ package org.jetbrains.kotlin.backend.konan.serialization
 import org.jetbrains.kotlin.backend.common.LoggingContext
 import org.jetbrains.kotlin.backend.common.serialization.*
 import org.jetbrains.kotlin.backend.common.serialization.signature.IdSignatureSerializer
+import org.jetbrains.kotlin.backend.konan.ir.interop.IrProviderForCEnumAndCStructStubs
 import org.jetbrains.kotlin.descriptors.DeclarationDescriptor
 import org.jetbrains.kotlin.ir.declarations.IrFile
 import org.jetbrains.kotlin.ir.descriptors.IrBuiltIns
@@ -18,6 +19,15 @@ class KonanIrModuleSerializer(
     private val signaturer = IdSignatureSerializer(KonanManglerIr)
     private val globalDeclarationTable = KonanGlobalDeclarationTable(signaturer, irBuiltIns)
 
+    // We skip files with IR for C structs and enums because they should be
+    // generated anew.
+    //
+    // See [IrProviderForCEnumAndCStructStubs.kt#L31] on why we generate IR.
+    // We may switch from IR generation to LazyIR later (at least for structs; enums are tricky)
+    // without changing kotlin libraries that depend on interop libraries.
+    override fun backendSpecificFileFilter(file: IrFile): Boolean =
+            file.fileEntry.name != IrProviderForCEnumAndCStructStubs.cTypeDefinitionsFileName
+
     override fun createSerializerForFile(file: IrFile): KonanIrFileSerializer =
             KonanIrFileSerializer(logger, DeclarationTable(globalDeclarationTable), expectDescriptorToSymbol, skipExpects = skipExpects)
 }