[NI] Fix shouldRunCompletion for builder inference session

#KT-41308 Fixed
#KT-41363

compiler/testData/codegen/box/builderInference/callableReferenceAndCoercionToUnit.kt

@@ -0,0 +1,20 @@
+// IGNORE_BACKEND: JS_IR
+// IGNORE_BACKEND_FIR: JVM_IR
+// !LANGUAGE: +NewInference
+// !DIAGNOSTICS: -EXPERIMENTAL_API_USAGE_ERROR -UNUSED_EXPRESSION
+// WITH_RUNTIME
+
+@OptIn(ExperimentalStdlibApi::class)
+fun test(s: String?): Int {
+    val list = buildList {
+        s?.let(::add)
+    }
+    return list.size
+}
+
+fun box(): String {
+    return when (test("hello")) {
+        1 -> "OK"
+        else -> "Error"
+    }
+}