[IR BE common] Use Descriptor-based IR only in CheckIrElementVisitor

compiler/ir/backend.common/build.gradle.kts

@@ -16,11 +16,3 @@ sourceSets {
     "test" {}
 }
 
-tasks {
-    val compileKotlin by existing(org.jetbrains.kotlin.gradle.tasks.KotlinCompile::class) {
-        kotlinOptions {
-            freeCompilerArgs += "-Xopt-in=org.jetbrains.kotlin.ir.DescriptorBasedIr"
-        }
-    }
-}
-

compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/CheckIrElementVisitor.kt

@@ -18,6 +18,7 @@ package org.jetbrains.kotlin.backend.common
 
 import org.jetbrains.kotlin.descriptors.CallableMemberDescriptor
 import org.jetbrains.kotlin.descriptors.Visibilities
+import org.jetbrains.kotlin.ir.DescriptorBasedIr
 import org.jetbrains.kotlin.ir.IrElement
 import org.jetbrains.kotlin.ir.declarations.*
 import org.jetbrains.kotlin.ir.descriptors.IrBuiltIns
@@ -31,6 +32,7 @@ import org.jetbrains.kotlin.resolve.descriptorUtil.isEffectivelyExternal
 
 typealias ReportError = (element: IrElement, message: String) -> Unit
 
+@OptIn(DescriptorBasedIr::class)
 class CheckIrElementVisitor(
     val irBuiltIns: IrBuiltIns,
     val reportError: ReportError,