[Native][tests] Move golden data outside of Gradle build file

kotlin-native/backend.native/tests/link/testLib_explicitly1.kt

@@ -0,0 +1,8 @@
+/*
+ * 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.
+ */
+
+fun main(args: Array<String>) {
+    println("Hello")
+}