[PLUGIN API] Add extension point to customize linkage process

compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/extensions/IrGenerationExtension.kt

@@ -7,8 +7,9 @@ package org.jetbrains.kotlin.backend.common.extensions
 
 import org.jetbrains.kotlin.extensions.ProjectExtensionDescriptor
 import org.jetbrains.kotlin.ir.declarations.IrModuleFragment
+import org.jetbrains.kotlin.ir.linkage.IrDeserializer
 
-interface IrGenerationExtension {
+interface IrGenerationExtension : IrDeserializer.IrLinkerExtension {
     companion object :
         ProjectExtensionDescriptor<IrGenerationExtension>(
             "org.jetbrains.kotlin.irGenerationExtension", IrGenerationExtension::class.java

compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/linkage/IrDeserializer.kt

@@ -5,10 +5,16 @@
 
 package org.jetbrains.kotlin.ir.linkage
 
+import org.jetbrains.kotlin.ir.declarations.IrDeclaration
 import org.jetbrains.kotlin.ir.declarations.IrModuleFragment
+import org.jetbrains.kotlin.ir.symbols.IrSymbol
 
 interface IrDeserializer : IrProvider {
 
+    interface IrLinkerExtension {
+        fun resolveSymbol(symbol: IrSymbol): IrDeclaration? = null
+    }
+
     fun init(moduleFragment: IrModuleFragment?) {}
     fun postProcess() {}
 }