Android: Upgraded the example to work with Gradle

examples/android/app/build.gradle

@@ -0,0 +1,39 @@
+apply plugin: 'com.android.application'
+
+android {
+    compileSdkVersion 27
+    defaultConfig {
+        applicationId "org.sfmldev.android"
+        minSdkVersion 19
+        targetSdkVersion 23
+        versionCode 1
+        versionName "1.0"
+        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
+        externalNativeBuild {
+            ndkBuild {
+                cppFlags "-std=c++14 -frtti -fexceptions"
+            }
+
+        }
+        ndk {
+            abiFilters 'armeabi-v7a'
+        }
+
+    }
+    buildTypes {
+        release {
+            minifyEnabled false
+            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
+        }
+    }
+    externalNativeBuild {
+        ndkBuild {
+            path "src/main/cpp/Android.mk"
+
+        }
+    }
+}
+
+dependencies {
+    implementation fileTree(dir: 'libs', include: ['*.jar'])
+}