IR: use String instead of FqName in IdSignature.PublicSignature

See https://github.com/JetBrains/kotlin/commit/3154eca218d

(cherry picked from commit de54f9897c589d8111b55a8d5069277a94dd8c39)

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

@@ -180,7 +180,7 @@ internal class KonanIrLinker(
 
         private fun resolveDescriptor(idSig: IdSignature): ClassDescriptor =
             with(idSig as IdSignature.PublicSignature) {
-                val classId = ClassId(packageFqn, declarationFqn, false)
+                val classId = ClassId(packageFqName(), FqName(declarationFqName), false)
                 moduleDescriptor.findClassAcrossModuleDependencies(classId) ?: error("No declaration found with $idSig")
             }
 
@@ -231,4 +231,4 @@ internal class KonanIrLinker(
                     .filter { !it.key.isForwardDeclarationModule && it.value.moduleDescriptor !== currentModule }
                     .forEach { this.put(it.key.konanLibrary!!.libraryName, it.value.moduleFragment) }
         }
-}
+}