[Tests] Migrate backend-independent tests from native to compiler/testData.

^KT-65979

compiler/testData/codegen/box/inline/coercionToUnit.kt

@@ -0,0 +1,22 @@
+/*
+ * Copyright 2010-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license
+ * that can be found in the LICENSE file.
+ */
+// WITH_STDLIB
+
+import kotlin.test.*
+
+fun <T> myRun(action: () -> T): T = action()
+
+fun foo(n: Number, b: Boolean) {
+    n.let {
+        if (b) return@let
+
+        myRun() { 42 }
+    }
+}
+
+fun box(): String {
+    assertEquals(Unit, foo(42, false))
+    return "OK"
+}