title: Android Studio IDE can't find NDK header files
body: <p>I'm using OpenGL ES2 inside an android app inside C++ code.
  Compiling and executing the program works as planned, however the IDE itself cannot find the NDK header files leaving my code files ugly:</p>
  
  <p><a href="https://i.stack.imgur.com/A324O.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/A324O.png" alt="Code file with include errors"></a></p>
  
  <p>My cmake file:</p>
  
  <pre><code>cmake_minimum_required(VERSION 3.4.1)
  add_library(native-lib
           SHARED
           openGLRenderer.cpp
           androidInterface.cpp
              )
  target_link_libraries(native-lib
                     android
                     log
                     EGL
                     GLESv2
                      )
  </code></pre>
  
  <p>build.gradle:</p>
  
  <pre><code>    ...
      externalNativeBuild {
          cmake {
              cppFlags "-frtti"
              arguments '-DANDROID_PLATFORM=android-21',
                      '-DANDROID_TOOLCHAIN=clang', '-DANDROID_STL=gnustl_static'
          }
  </code></pre>
  
  <p>...</p>
  
  <pre><code>    externalNativeBuild {
      cmake {
          path "src/main/cpp/CMakeLists.txt"
      }
  }
  </code></pre>
  
  <p>What do I have to do to fix this? Thank you!</p>