[K/N] Add trivial test for llvm.objc.clang.arc.use lowering

kotlin-native/backend.native/tests/interop/objc_arc_contract/main.kt

@@ -0,0 +1,10 @@
+/*
+ * Copyright 2010-2021 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+// We don't do anything meaningful here, because the test is actually checks
+// how compiler handles external bitcode (see main.ll). So this file is needed only for compiler invocation.
+fun main() {
+    println("ok")
+}

kotlin-native/backend.native/tests/interop/objc_arc_contract/main.ll

@@ -0,0 +1,9 @@
+; Prevent function from DCE
+@llvm.compiler.used = appending global [1 x i8*] [ i8* bitcast (void (i8*, i8*)* @test to i8*) ], section "llvm.metadata"
+
+declare void @llvm.objc.clang.arc.use(...) nounwind
+
+define void @test(i8* %a, i8* %b) {
+  call void (...) @llvm.objc.clang.arc.use(i8* %a, i8* %b) nounwind
+  ret void
+}