IR: create shared variables for val-variables when needed

This is possible when a lambda's contract guarantees initialization of a
variable.

compiler/testData/codegen/boxInline/contracts/complexInitializerWithStackTransformation.kt

@@ -1,9 +1,9 @@
 // !LANGUAGE: +AllowContractsForCustomFunctions +UseCallsInPlaceEffect +ReadDeserializedContracts
 // !USE_EXPERIMENTAL: kotlin.contracts.ExperimentalContracts
-// IGNORE_BACKEND: JVM_IR
-// IGNORE_BACKEND_MULTI_MODULE: JVM_IR
 // IGNORE_BACKEND: NATIVE
+
 // FILE: 1.kt
+
 package test
 
 import kotlin.contracts.*
@@ -28,4 +28,4 @@ fun box(): String {
         x = try { test("OK") } catch (e: Exception) { test("fail") }
     }
     return x
-}
+}