Update Android Docs w/ NDK installation and troubleshooting (keybase#…

…20716)

* Update running.md

* Add NDK installation steps

* Updated solution

shared/docs/android/running.md

@@ -69,6 +69,18 @@ Same as below.
 `yarn rn-build-clean-android`
 
 
+## `$HOME/.../Android/sdk/ndk-bundle` Does not point to an Android NDK
+
+### macOS
+
+If you're hitting this issue, it is because you either don not have an NDK installed or installed an NDK with an older version of Android Studio that created an old directory path.
+
+Android Studio 3.5.0 and later seem to install ndk versions at the following path: `~/Library/Android/sdk/ndk/{version}`
+
+To resolve this issue, use the `sdkmanager` to re-install `ndk-bundle` at the correct directory path. 
+
+[Instuctions can be found here](./setup.md)
+
 ## Hot reloading / File Watching
 
 ### Linux

shared/docs/android/setup.md

@@ -4,6 +4,20 @@ Follow instructions for "Building Projects with Native Code" at
 https://facebook.github.io/react-native/docs/getting-started.html to
 install and configure Android.
 
+### Installing an NDK version
+Additionally an `NDK` version needs to be installed for `yarn rn-gobuild-android` to work.
+
+**With Android Studio**
+You will already have the `sdkmanager` command line tool installed. So run:
+
+`sdkmanager --install "ndk-bundle"` which should write to `$HOME/Library/Android/sdk/ndk-bundle` on macOS.
+
+**Without Android Stuido** 
+You will need the Android Studio Command Line Tools to use `sdkmanager` without Android Studio.
+[Download Command Line Tools](https://developer.android.com/studio/index.html#command-tools) here.
+
+Then run `sdkmanager --install "ndk-bundle"` which should write to `$HOME/Library/Android/sdk/ndk-bundle` on macOS.
+
 ## Emulator Setup
 
 ### macOS