Add AnalysisFlags.metadataCompilation flag

It's `true` if metadata compilation mode is activated

It's being initialized in K2MetadataCompilerArguments

compiler/cli/cli-common/src/org/jetbrains/kotlin/cli/common/arguments/K2MetadataCompilerArguments.kt

@@ -16,7 +16,11 @@
 
 package org.jetbrains.kotlin.cli.common.arguments
 
+import org.jetbrains.kotlin.cli.common.messages.MessageCollector
+import org.jetbrains.kotlin.config.AnalysisFlag
+import org.jetbrains.kotlin.config.AnalysisFlags
 import org.jetbrains.kotlin.config.LanguageFeature
+import org.jetbrains.kotlin.config.LanguageVersion
 
 class K2MetadataCompilerArguments : CommonCompilerArguments() {
     companion object {
@@ -83,6 +87,11 @@ class K2MetadataCompilerArguments : CommonCompilerArguments() {
 
     override fun copyOf(): Freezable = copyK2MetadataCompilerArguments(this, K2MetadataCompilerArguments())
 
+    override fun configureAnalysisFlags(collector: MessageCollector, languageVersion: LanguageVersion): MutableMap<AnalysisFlag<*>, Any> =
+        super.configureAnalysisFlags(collector, languageVersion).also {
+            it[AnalysisFlags.metadataCompilation] = true
+        }
+
     override fun configureExtraLanguageFeatures(map: HashMap<LanguageFeature, LanguageFeature.State>) {
         map[LanguageFeature.MultiPlatformProjects] = LanguageFeature.State.ENABLED
     }

compiler/config/src/org/jetbrains/kotlin/config/AnalysisFlags.kt

@@ -9,6 +9,9 @@ object AnalysisFlags {
     @JvmStatic
     val skipMetadataVersionCheck by AnalysisFlag.Delegates.Boolean
 
+    @JvmStatic
+    val metadataCompilation by AnalysisFlag.Delegates.Boolean
+
     @JvmStatic
     val skipPrereleaseCheck by AnalysisFlag.Delegates.Boolean