Buck - java.lang.UnsatisfiedLinkError: couldn't find "libjni.so". How to solve it?

A runtime exception is happening after executing the command buck install --run demo_app_android following this tutorial and this sample demo

Then, the following is shown in console

Installing apk on emulator-5554 (null).
[-] PROCESSING BUCK FILES...FINISHED 0.0s [100%] 🐌  File removed
[-] DOWNLOADING... (0.00 B/S AVG, TOTAL: 0.00 B, 0 Artifacts)
[-] BUILDING...FINISHED 0.8s [100%] (1/1 JOBS, 1 UPDATED, 0 [0.0%] CACHE MISS)
[+] INSTALLING...2.1s
Successfully ran install apk //android:demo-app on 1 device(s)
Starting activity com.facebook.buck.demo/.App...
Successfully ran start activity on 1 device(s)

Finally, the device shows a message saying Buck Demo App has stopped The app was successfully installed as I can see it on the apps list but it's not working

Stacktrace:

E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.facebook.buck.demo, PID: 7265
    java.lang.UnsatisfiedLinkError: dalvik.system.PathClassLoader[DexPathList[[zip file "/data/app/com.facebook.buck.demo-1/base.apk"],nativeLibraryDirectories=[/data/app/com.facebook.buck.demo-1/lib/x86, /system/lib, /vendor/lib]]] couldn't find "libjni.so"
    at java.lang.Runtime.loadLibrary0(Runtime.java:972)
    at java.lang.System.loadLibrary(System.java:1530)
    at com.facebook.buck.demo.Hello.<init>(Hello.java:13)
    at com.facebook.buck.demo.App.onCreate(App.java:24)
    at android.app.Activity.performCreate(Activity.java:6662)
    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1118)
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2599)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2707)
    at android.app.ActivityThread.-wrap12(ActivityThread.java)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1460)
    at android.os.Handler.dispatchMessage(Handler.java:102)
    at android.os.Looper.loop(Looper.java:154)
    at android.app.ActivityThread.main(ActivityThread.java:6077)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:866)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:756)

Device specs:

Native Android Emulator (also, ran it into a real device with same result)
Nexus 5 API 24

My computer:

MacBook pro mid 2012

Note: Also, this issue was reported directly to the buck repository but no solution was given yet

Any idea about how to solve it?

Solution

Repeating the answer from github:

You need to install Android NDK from here (version 10e) and set ANDROID_NDK_REPOSITORY to the location of the unpacked NDK (see buckconfig section for more info).

For example, if you unpack NDK to ~/tmp/ndk (so that there is a directory ~/tmp/ndk/android-ndk-r10e), you need to set ANDROID_NDK_REPOSITORY to ~/tmp/ndk.

After that delete old cache and rebuild the app:

$ buck kill && rm -rf buck-out
$ buck build demo_app_android