[KLIB] Use -Xmetadata-klib to produce metadata KLIBs

With this change a new `-Xmetadata-klib` CLI flag becomes the
preferable way to instruct K2MetadataCompiler to produce metadata
KLIBs. The old `-Xexpect-actual-linker` flag still works for
K2MetadataCompiler, but that would last just for a short transition
period until the necessary changes are made in the Gradle plugin.

The K2NativeCompiler does not work anymore with `-Xexpect-actual-linker`
and respects only the `-Xmetadata-klib` flag. This is not an
issue since the Gradle plugin anyway supplies both flags for Native
metadata compilations.

^KT-61136

kotlin-native/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/driver/phases/Serializer.kt

@@ -36,7 +36,6 @@ internal val SerializerPhase = createSimpleNamedCompilerPhase<PhaseContext, Seri
         outputIfNotEnabled = { _, _, _, _ -> SerializerOutput(null, null, null, emptyList()) }
 ) { context: PhaseContext, input: SerializerInput ->
     val config = context.config
-    val expectActualLinker = config.configuration.get(CommonConfigurationKeys.EXPECT_ACTUAL_LINKER) ?: false
     val messageLogger = config.configuration.get(IrMessageLogger.IR_MESSAGE_LOGGER) ?: IrMessageLogger.None
     val relativePathBase = config.configuration.get(CommonConfigurationKeys.KLIB_RELATIVE_PATH_BASES) ?: emptyList()
     val normalizeAbsolutePaths = config.configuration.get(CommonConfigurationKeys.KLIB_NORMALIZE_ABSOLUTE_PATH) ?: false
@@ -55,11 +54,14 @@ internal val SerializerPhase = createSimpleNamedCompilerPhase<PhaseContext, Seri
     }
 
     val serializer = KlibMetadataMonolithicSerializer(
-        config.configuration.languageVersionSettings,
-        config.configuration.get(CommonConfigurationKeys.METADATA_VERSION)!!,
-        config.project,
-        exportKDoc = context.shouldExportKDoc(),
-        !expectActualLinker, includeOnlyModuleContent = true, produceHeaderKlib = input.produceHeaderKlib)
+            languageVersionSettings = config.configuration.languageVersionSettings,
+            metadataVersion = config.configuration.get(CommonConfigurationKeys.METADATA_VERSION)!!,
+            project = config.project,
+            exportKDoc = context.shouldExportKDoc(),
+            skipExpects = !config.metadataKlib,
+            includeOnlyModuleContent = true,
+            produceHeaderKlib = input.produceHeaderKlib
+    )
     val serializedMetadata = serializer.serializeModule(input.moduleDescriptor)
     val neededLibraries = config.librariesWithDependencies()
     SerializerOutput(serializedMetadata, serializedIr, null, neededLibraries)