title: DllNotFoundException for Unity3d Android c++
body: <p>I'm building a very simple c++ Shared Library in Android Studio, and using CMAKE to build .so for x86, x86_64, armeabi-v7a, arm64-v8a</p>
  
  <p>The resulting files are called <code>libnative-lib.so</code></p>
  
  <p>I'm using Unity3D (2018.3.11f1). and the .so files are copied to Plugins/Android_x86, Plugins/Android_x86_64, Plugins/Android_armeabi-v7a, Plugins/Android_arm64-v8a.</p>
  
  <p>Each of the plugins shows with correct settings in the inspector preview</p>
  
  <p>My C++</p>
  
  <pre class="lang-cpp prettyprint-override"><code>extern "C" int initTest() {
      return -1;
  }
  </code></pre>
  
  <p>my c# (calling the plugin 'native-lib' which is consistent with <a href="https://docs.unity3d.com/Manual/AndroidNativePlugins.html" rel="nofollow noreferrer">advice at the Unity3D manual</a> and elsewhere)</p>
  
  <pre class="lang-cs prettyprint-override"><code>    [DllImport("native-lib", CallingConvention = CallingConvention.Cdecl)]
      public static extern int initTest();
      // Start is called before the first frame update
      void Start()
      {
          Debug.Log(initTest());
      }
  </code></pre>
  
  <p>It always results in DllNotFoundException error</p>
  
  <blockquote>
    <p>DllNotFoundException: native-lib</p>
  </blockquote>