Android: add x86 builds

android/app/build.gradle

@@ -11,7 +11,7 @@ android {
         externalNativeBuild {
             ndkBuild {
                 arguments "NDK_APPLICATION_MK:=../jni/Application.mk"
-                abiFilters "armeabi-v7a"
+                abiFilters "armeabi-v7a", "x86"
             }
         }
     }

android/jni/Application.mk

@@ -1,3 +1,3 @@
 APP_STL := stlport_static
-APP_ABI := armeabi-v7a
+APP_ABI := armeabi-v7a x86
 APP_PLATFORM := android-9