title: Gradle NDK to specify an 'include' directive in generated Android.mk
body: <p>When you have </p>
  
  <pre><code>android {
    defaultConfig {
      ndk {
                  moduleName "yourlib"
                  stl "stlport_static"
                  ldLibs "log", "z", "m"
                  cFlags "-I/some/include/dir/"
          }
      ...
    }
    ...
  }
  </code></pre>
  
  <p>in your build.gradle then Gradle will compile the files in src/main/jni/ and it will generate an Android.mk in build/ndk/debug/Android.mk.</p>
  
  <p>However, in my case, I'm trying to compile some C++ files compiled against OpenCV.</p>
  
  <p>I have this working when I manually create the Android.mk file and run the ndk-build command. But I want to do it via Gradle / Android Studio automatically.</p>
  
  <p>When doing this manually, I include the libraries to link against. I do this, in the manually created Android.mk, with the line:</p>
  
  <pre><code>include /path/to/the/opencv/directory/sdk/native/jni/OpenCV.mk
  </code></pre>
  
  <p>However, in Android's Gradle plugin, I am unsure of how to add this 'include' directive in the generated Android.mk file.</p>
  
  <p>Can anyone point me in the right Gradle-directive direction to add this line to the generate file? Thanks.</p>